Method for determining visual sharpness characteristic of test object, use of adapted sighting target and device

Abstract

In a method for determining a visual sharpness characteristic of a test subject having at least one astigmatic visual impairment, visual impairment data of the test subject are provided, the visual impairment data containing at least one axial position of a desired optical cylindrical correction. Selecting a priority direction (V1; v2) such that the priority direction (V1; v2) either corresponds to an axis position associated with the optical cylindrical correction or is rotated by 90 degrees relative to the axis position. Alternatively, a priority direction may be derived from the wavefront data by a point spread function. The optical effect is applied at least in a selected preferred direction. At least one adapted sighting target having a pointing feature is shown, the adapted sighting target being shown in an oriented manner such that the pointing feature thereof is parallel to the priority direction (V1; v2) is provided. Taking into account at least one dimension of the pointing feature of the adapted sighting target and the applied optical effect, for the selected preferred direction (V1; and V2) determining the visual acuity characteristic of the test object.

Description

Field of the Invention

[0001] The present invention relates to a method, an adapted use of a visual target, and an apparatus for determining visual acuity characteristics of a test subject. Background Art

[0002] Determining visual acuity as a visual acuity characteristic of a test subject with a visual defect, in particular an astigmatic visual defect, is a core task of optometry. The astigmatic visual defect of the test subject can be compensated in such a way that, in addition to a possible required optical spherical correction, an optical cylindrical correction is provided to and / or applied to the test subject.

[0003] Known methods for determining the visual acuity of a test subject with an astigmatic visual defect are usually time-consuming, associated with high costs, and / or error-prone because they are usually based on the active feedback of the test subject. In addition, in order to determine visual acuity, it is necessary to compensate for the astigmatic visual defect of the test subject by providing an optical cylindrical correction and an optical spherical correction, for example, with the aid of a phoropter or test glasses.

[0004] Providing the optical cylindrical correction in front of the test glasses or phoropter is cumbersome and requires space. Therefore, the test glasses or phoropter can only be combined with another device, such as an eye tracker, with difficulty here.

[0005] Without providing the required cylindrical correction to the test subject in the optical unit used, the astigmatic visual defect cannot be compensated.

[0006] Therefore, in the test subject, visual acuity cannot usually be determined within the relevant range or only distorted visual acuity can be determined, especially if the test subject has a significant cylindrical defect. Summary of the Invention

[0007] The object of the present invention is to simply and reliably determine the visual acuity characteristics of a test subject with an astigmatic visual defect.

[0008] This object is solved by the subject matter of the independent claims. Preferred embodiments are the subject matter of the dependent claims.

[0009] One aspect relates to a method for determining the visual acuity characteristics of a test subject having at least one astigmatic vision defect. Here, vision defect data of the test subject is provided, wherein the vision defect data includes at least one axis position of the required optical cylindrical correction. A preferred direction is selected such that the preferred direction either corresponds to the axis position assigned to the optical cylindrical correction or is rotated 90° relative to the axis position. Alternatively, the preferred direction can be derived from the wavefront data by means of a point spread function. An optical effect is applied at least in the selected preferred direction. At least one adapted visual target having a pointing feature is shown, wherein the adapted visual target is shown orientationally such that the pointing feature is arranged parallel to the preferred direction. Finally, the visual acuity characteristics of the test subject are determined for the selected preferred direction taking into account at least one dimension of the pointing feature of the adapted visual target and the applied optical effect.

[0010] The visual acuity characteristics of the test subject can be determined for one eye of the test subject, determined separately (i.e., monocularly) for both eyes, or determined together (i.e., binocularly) for both eyes. Preferably, the visual acuity characteristics are determined separately monocularly for each eye of the test subject.

[0011] The test subject has an astigmatic vision defect and thus requires an optical cylindrical correction that corrects and / or reduces the vision defect of the test subject. Typically, a person with an astigmatic vision defect additionally requires an optical spherical correction that is combined with the optical cylindrical correction. For example, these optical corrections can be integrated into the test subject's spectacle lenses and / or contact lenses and / or intraocular lenses.

[0012] The applied optical effect can be achieved by providing an optical corrector (such as a lens) in front of the corresponding eye of the test subject. With the optical correction, the light incident on the test subject's eye is manipulated. Thus, the optical correction can correspond to the applied optical effect, in particular an optical effect having spherical and / or cylindrical optical effects.

[0013] To select the preferred direction, first the vision defect data of the test subject is required. The vision defect data may have been determined, for example, in the context of subjective and / or objective refraction. The vision defect data can exist as prescription data of the test subject. The method for determining visual acuity can be integrated into the objective and / or subjective refraction determination and / or can be performed subsequently.

[0014] The vision defect data includes at least the axis position of the required optical cylindrical correction. In addition, the vision defect data can also include the strength of the required optical cylindrical correction. The vision defect data can also include the required optical spherical correction, the required toric correction, and / or the axis position assigned to the cylindrical correction of the toric.

[0015] Alternatively, the vision defect data can be based on wavefront analysis and on the wavefront data thus determined.

[0016] Based on the vision defect data, in particular based on the assigned axis position, a preferred direction is selected. As the preferred direction, the axis position can be used directly, or a direction rotated by 90° relative to this axis position can be used.

[0017] If the vision defect data is based on wavefront data, then the preferred direction can also be derived from the wavefront data via the point spread function. Here, the preferred direction can be derived from the point spread function calculated based on the wavefront data. Here, for example, the direction and / or axis of the minimum extent of the point spread function can be selected as the preferred direction. Here, the direction of minimum confusion, for example the direction of the minimum standard deviation of the point spread function, can be selected.

[0018] The axis position is usually arranged in a plane that is approximately perpendicular to the selected line of sight direction of the test object. As the line of sight direction, for example, the line of sight direction of the test object in the use position can be selected, which is defined in the relevant standard for this purpose. The axis position line is arranged and / or defined in a plane that is approximately perpendicular to the use position. Here, the axis position can in particular be arranged in the plane of the spectacle lens and / or contact lens on which the test object is arranged. Thus, the axis position can in particular coincide with the axis of the optical cylindrical correction that should be integrated into the spectacle lens and / or contact lens for the test object.

[0019] If the axis position is directly selected as the preferred direction, then the preferred direction is arranged approximately in the first principal meridian of the required optical cylindrical correction and additionally arranged approximately perpendicular to the line of sight direction of the test object.

[0020] If a direction rotated by 90° relative to the axis position is selected as the preferred direction, then the rotation by 90° takes place in a plane that is approximately perpendicular to the line of sight direction of the test object. Here, the selected preferred direction can be arranged approximately in the second principal meridian of the required optical cylindrical correction and can also be approximately perpendicular to the line of sight direction of the test object.

[0021] After the preferred direction has been selected as described, an optical effect is applied at least in the selected preferred direction. Here, for example, a rotationally symmetric optical lens, such as an optical spherical correction, can be provided. In particular, the following optical spherical correction can be applied, which at least partially corrects the vision defect of the test object in the selected preferred direction according to the vision defect data.

[0022] If the axis position for the desired optical cylindrical correction is selected, i.e., the first principal meridian of the cylindrical correction as the preferred direction, then as an optical effect, an optical spherical correction can be used, for example, whose amplitude exactly corresponds to the desired spherical correction included in the visual defect data, regardless of the cylindrical error of the test subject.

[0023] If a direction rotated by 90° relative to the axis position is selected, i.e., the second principal meridian of the cylindrical correction as the preferred direction, then as an optical effect, an optical spherical correction can be applied, for example, whose amplitude is produced by the sum of the spherical correction stored in the visual defect data plus the cylindrical correction stored there (for example, both are expressed in diopters). When forming the sum, the signs of the desired spherical correction and the desired cylindrical correction are to be considered.

[0024] If the visual defect data contains the desired spherical correction s and the desired cylindrical correction z (sometimes also abbreviated as c), then a correction with the value s can be applied as an optical effect for the first principal meridian, and a correction with the value s + z can be applied as an optical effect for the second principal meridian.

[0025] The application of the optical effect can be achieved by providing the mentioned optical effect to at least one eye of the test subject. This can be achieved, for example, by physically providing a corresponding optical lens, such as by means of measurement glasses and / or through a refractive unit. In an alternative approach, the application of the optical effect is achieved non - physically, but it can be simulated within the scope of wavefront simulation. Thus, the exact type of application may depend on the refractive unit used here.

[0026] To apply the optical effect at least in the selected preferred direction, an optical spherical effect, such as a rotationally symmetric lens, is preferably used. This produces the desired optical effect not only in the selected preferred direction but even over the entire sphere. Here, the optical spherical effect can also be simulated virtually.

[0027] Using the thus - applied optical effect, at least for the selected preferred direction, the visual defect of the test subject can be at least partially corrected.

[0028] It should be noted here that an optical cylindrical correction is not required to determine the visual acuity characteristics. It is sufficient to determine the visual acuity characteristics in the case of applying and / or providing (for example) a pure optical spherical correction without an optical cylindrical correction for the method.

[0029] Applying an optical spherical correction as an optical effect is generally easier to implement than applying an optical cylindrical correction, for example, because the axis position does not have to be considered for spherical correction. Thus, the method is simplified by omitting the optical cylindrical correction.

[0030] As a visual acuity characteristic, for example, at least one visual acuity and / or the sensitivity of the test object and / or a visual acuity - correction value pair and / or at least one refractive value can be determined in the applied optical effect. When the relevant correction is applied as an optical effect for at least the selected preferred direction, the visual - sensitivity correction value pair contains information about the visual acuity of the test object. In this regard, the visual acuity - correction value pair can additionally also contain the associated preferred direction.

[0031] The determination of visual acuity based on optotypes (such as optometric fonts) is known in principle. However, according to the present invention, now not only normal and unadapted standard optotypes are used, but also adapted optotypes that are adapted to the selected preferred direction and thus to the visual defect of the test object. Optotypes with a pointing feature are suitable for this purpose.

[0032] Here, the adapted optotype has a feature with an orientation as the pointing feature that the test object should recognize within the scope of the visual task. Optotypes with a pointing feature, such as Landolt rings or Snellen - Es, are known in principle. However, Landolt rings are, for example, standardly oriented such that the gap of the corresponding Landolt ring can be arranged exactly at 0°, 90°, 180°, etc.

[0033] Different from this commonly common arrangement of the gap of the Landolt ring as an optotype, now adapted optotypes are used whose pointing features are arranged precisely and / or as precisely as possible parallel to the selected preferred direction. If the axis position assigned to the required optical cylindrical correction is, for example, exactly 12°, or generally exactly the angle α, and if this axis position is selected as the preferred direction, then the adapted optotype is arranged such that its pointing feature is shown at exactly an angle of 12°, generally at the angle α. Thus, the optotype is precisely adapted to the selected preferred direction for which the applied optical spherical correction well corrects the visual defect of the test object.

[0034] What the arrangement of the pointing feature of the adapted optotype in the preferred direction can achieve for the test object is that even when the test object is not fully corrected, i.e., not even corrected cylindrically, the test object can still recognize this feature of the adapted optotype. Even when the test object cannot fully and clearly recognize the adapted optotype (because its astigmatism is not corrected by the optical cylindrical correction), the test object can still at least recognize the pointing feature with a corresponding sufficient visual acuity. Thus, when the test object is optimally and / or at least sufficiently corrected in the preferred direction by the applied optical effect, the adapted optotype enables the test object to at least recognize the pointing feature of the adapted optotype.

[0035] Finally, taking into account at least one dimension of the orientation feature of the adapted visual target, the visual acuity and / or visual sharpness characteristics of the test subject can be determined for the selected preferred direction. The determination of visual acuity can be carried out in a common manner here, namely based on the dimension of the orientation feature that the test subject can just still recognize and / or identify in the applied optical effect.

[0036] To obtain the dimensions required for visual acuity calculation, a plurality of adapted visual targets that differ in the dimension of the orientation feature can be shown to the test subject successively and / or simultaneously. Within the scope of at least one visual task, the test subject can be required to recognize at least one adapted visual target.

[0037] Within the scope of the visual task and / or visual task sequence, at least one adapted visual target can be shown, for example, increasingly smaller, such that the visual task gradually becomes more difficult. Alternatively, adapted visual targets of different dimensions can also be shown simultaneously. What can be obtained here is up to which dimension design of the orientation feature the test subject can still recognize the adapted visual target.

[0038] The visual defect data required by the test subject in this method can, for example, correspond to the best correction and / or best refraction required by the test subject to correct their visual defect. Additionally or alternatively, the visual defect data can also deviate slightly from the required best optical correction. For example, the visual defect data can correspond to the data obtained from the objective refractive measurement of the test subject. The objectively obtained refractive data generally corresponds very precisely to the axis position actually required by the test subject for cylindrical correction in the axis positions obtained here.

[0039] In addition to the best correction, an optically corrected that is slightly "blurred", i.e., changed, relative to the best correction can also be applied as an optical effect, for example, within the scope of determining the sensitivity of the test subject. Here, therefore, deliberately "deteriorated" visual defect data can also be used.

[0040] In a variant, the applied optical effect can be completely independent of the visual defect data of the test subject. Here, the dimension of the orientation feature of the shown adapted visual target can be kept constant, and instead, the applied optical effect can be varied for this constant dimension until the test subject can recognize (or can no longer recognize) the orientation feature of the adapted visual target. Thus, a visual acuity - correction value pair can be obtained that can be independent of the best correction (subjectively and / or objectively obtained).

[0041] However, in principle, when using the best optical correction required by the test subject in the selected preferred direction as the optical effect, the visual acuity determination can be determined most precisely as the visual sharpness characteristic for the selected preferred direction.

[0042] What the method can achieve is to determine the visual acuity characteristics, such as visual acuity, of a test subject without providing and / or applying optical cylindrical correction to the test subject. Instead, an adapted visual target is used, which is precisely adapted to the axial position of the required cylindrical correction and can thus render the application of optical cylindrical correction redundant. What this can achieve is to perform the determination of visual acuity characteristics using, for example, cheaper equipment that cannot itself apply any optical cylindrical correction.

[0043] In addition, what the method can achieve is to combine the refractive unit used with additional equipment, because overall, when the possibility of applying the required cylindrical correction can be dispensed with, more space is available for additional equipment. Thus, for example, a refractometer, especially an autorefractor, can be used as the refractive unit for applying optical effects.

[0044] In visual acuity measurement, the visual defect of the test subject can only be corrected for the selected preferred direction, but not for the principal meridian perpendicular to the required cylindrical correction.

[0045] As the adapted visual target, an optotype can be used, the lowest spatial frequency of which lies in the direction of the strongest uncorrected principal meridian, i.e., is oriented parallel to it. Alternatively or additionally, the highest spatial frequency of the optotype used can lie in the direction of the best-corrected principal meridian, i.e., is oriented parallel to it.

[0046] When using objective measurement and / or a combination of objective and subjective measurements to provide visual defect data, the axial position, i.e., the orientation, can be directly obtained from the objective data because the objective measurement of the axial position is usually very reliable. Compared with the measured visual defect data, the objectively measured cylinder, i.e., the objectively measured required optical cylindrical correction, can be reduced because the objectively measured cylinder is usually not fully accepted by the test subject. If necessary, the spherical equivalent should be calculated before adapting the cylinder power, and when calculating the principal meridians, the spherical equivalent should be obtained in place of the sphere.

[0047] According to an embodiment, the pointing feature of the adapted visual target has a sequence of bright and dark regions that follow one another along a preferred direction. For example, the sequence of bright and dark regions can be perpendicular to the hatching or to the orientation of the notch of the Landolt ring. Thus, perpendicular to the notch of the Landolt ring, after the dark circular edge, there is first a bright notch, followed by another dark circular edge. Thus, the pointing feature of the Landolt ring is arranged perpendicular to the notch. In the case of Snellen-E, the pointing feature is arranged perpendicular to the three parallel E-lines. Generally, the pointing feature can correspond to a sequence of at least one bright and one dark region, preferably interrupting the dark region at least by a bright region, or vice versa, interrupting the bright region at least by a dark region. Here, the bright and / or dark regions can be configured, for example, as lines and / or have edges oriented perpendicular to the preferred direction.

[0048] According to an embodiment, an unadapted standard visual target with a pointing feature is provided. The standard visual target is rotated in the display plane such that its pointing feature is arranged parallel to the preferred direction. Finally, the thus rotated standard visual target is shown as the adapted visual target. This showing can be achieved, in particular, on a screen within the display plane. Here, initially, an unadapted standard visual target can be assumed, which is rotated (for example, purely computationally, not shown here) such that it is arranged in the correct orientation with respect to the selected preferred direction. Thus, the adapted visual target is made from the unadapted standard visual target. Only after this internal calculation is the adapted visual target shown. As the display plane, for example, the following plane can be used, in which the screen can show the visual target. The display plane is preferably arranged approximately perpendicular to the line of sight of the test subject and / or approximately parallel to the selected preferred direction.

[0049] By using an initially unadapted standard visual target with a pointing feature, an adapted visual target can be provided in a simple manner and method from this unadapted standard visual target by rotation (for example, around the center point of the standard visual target and / or around other points within the display plane), which can be adapted to each arbitrary axial position of the required optical cylindrical correction. In addition, the adapted visual target can be scaled arbitrarily on the display such that, depending on the visual task currently presented to the test subject, the adapted visual target can be shown and / or displayed larger or smaller.

[0050] According to an embodiment, an axis position assigned to an optical cylindrical correction and arranged in a first principal meridian of the required optical cylindrical correction is selected as a first preferred direction, wherein an optical spherical correction is applied as an optical effect, which corrects the visual defect of the test object in the first principal meridian according to the visual defect data, and wherein, as a visual acuity characteristic, the visual acuity of the test object is determined for the first principal meridian. Alternatively or additionally, a direction rotated 90° relative to the axis position is selected as a second preferred direction, which is arranged in a second principal meridian of the required optical cylindrical correction, wherein an optical spherical correction is applied as an optical effect, which corrects the visual defect of the test object in the second principal meridian according to the visual defect data, and wherein, as a visual acuity characteristic, the visual acuity of the test object is determined for the second principal meridian. If the first preferred direction is selected, then the optical spherical correction stored in the visual defect data as the required optical spherical correction can be accurately applied as the optical spherical correction. If the second preferred direction, i.e., the second principal meridian, is selected, then the sum of the optical spherical correction stored in the visual defect data and the stored optical cylindrical correction can be selected as the optical spherical correction. This sum corresponds to the correction required by the test object in the second principal meridian. Thus, with the thus selected optical spherical correction, the visual defect of the test object is corrected relatively well and / or optimally at least in the selected preferred direction, i.e., in the selected principal meridian.

[0051] In an improvement, the visual acuity of the test object is determined for the first and second principal meridians of the required optical cylindrical correction, and therefrom a direction-independent visual acuity is derived. In other words, the first preferred direction is selected and the visual acuity of the test object is determined for the first principal meridian here, and the second preferred direction is selected and the visual acuity of the test object is determined for the second principal meridian. As a result of the visual acuity determination, the results for each principal meridian can initially be stated. In addition, a direction-independent visual acuity can be derived from these two visual acuity values. The direction-independent visual acuity can be stated, for example, as the highest value, the lowest value, the arithmetic mean, the geometric mean, the harmonic mean, the logarithmic mean, the quadratic mean, the cubic mean, or a combination of the selected values among the above values obtained during the measurement.

[0052] According to an embodiment, the visual acuity is determined only for one of the two principal meridians. Here, the better principal meridian is selected. As the better principal meridian, the following principal meridian can be selected, in which the required optical correction is arranged more in the positive direction, or more in the negative direction, or a stronger correction is required in absolute value, or a weaker correction is required in absolute value. It is also possible to select the principal meridian that is closer to the vertical line in terms of the axis position or the principal meridian whose axis position is closer to the horizontal line.

[0053] Generally, visual acuity can be understood as recognizability according to size, but also as recognizability according to other parameters shown, such as contrast. As visual acuity, recognizability according to size and contrast and / or a combination of other parameters among these parameters can also be used.

[0054] According to an embodiment, a Landolt ring with a notch shown rotated by 90° relative to a selected preferred direction is used as an adapted visual target. The orientation of the notch rotated by 90° relative to the selected preferred direction results in the dark-bright-dark sequence being precisely arranged along the selected preferred direction on the notch of the Landolt ring. Therefore, the pointing feature of the Landolt ring is precisely arranged parallel to the selected preferred direction, and the visual acuity of the selected preferred direction can be simply determined.

[0055] According to an embodiment, a Snellen-E with a connecting line connecting three parallel E-lines arranged parallel to the selected preferred direction is used as an adapted visual target. Here, the pointing feature of the Snellen-E is a sequence of three parallel E-lines, that is, for example, a sequence of bright (background), dark of the upper line, bright of the middle space, dark of the middle line, bright of the middle space, dark of the lower E-line, and finally bright of the background. This can also simply adapt the Snellen-E as a standard visual target to the preferred direction and thus use it as an adapted visual target.

[0056] In an improved embodiment, the adapted visual target is shown at least once rotated by 90° clockwise relative to the preferred direction and at least once rotated by 90° counterclockwise relative to the preferred direction. Here, within the scope of the visual task, the test subject is required to distinguish between these two differently rotated adapted visual targets. If the preferred direction is oriented approximately vertically upward, then the test subject may, for example, be required to distinguish whether the notch of the Landolt ring points to the left or to the right. This also applies to using the Snellen-E as the adapted visual target.

[0057] According to an embodiment, the shaded surface serves as an adapted visual target. In the shaded surface, the hatching lines are arranged perpendicular to the selected preferred direction. A figure, such as a circle, rectangle, symbol, animal, letter, etc., can be used as the shaded surface, for example. The figure is configured to be filled with shading. Here, the figure preferably does not have any boundary lines that may interfere with the shading, but is only configured as a borderless figure filled with shading. Here, the hatching lines are shown perpendicular to the preferred direction because the relevant feature of the pointing feature as a visual target here is the continuity of the light and dark alternating areas of the shading. It may be advantageous here for the figure itself to be configured as uniform as possible and have few details, i.e., configured as a circle or a square, for example. Here, it is preferred that the figure is configured as simple and with few details as possible. To adapt the orientation of the pointing feature, the entire visual target including the shading can be rotated and / or turned, or only the shading within the constant surface and / or figure can be rotated and / or turned. Here, the shading can be configured as binary, i.e., having hard black and / or white edges, or can be configured with continuous curves. The shading can be configured with continuous curves, for example, configured with a sinusoidal intensity curve or a similar intensity curve.

[0058] According to an embodiment, in addition to the adapted visual target, at least one further visual target is shown, whose gray value roughly corresponds to the average gray value of the adapted visual target, and within the scope of the visual task, the test subject is required to distinguish the shown visual targets from each other. Instead of a visual target with an average gray value, a visual target (such as the adapted visual target) whose shading is not perpendicular to the selected preferred direction but parallel to the preferred direction can also be used. Such a visual target appears as a substantially gray visual target perpendicular to the preferred direction for the test subject due to their astigmatic vision defect that is wrongly corrected for this shading orientation. Within the scope of the visual task, on the display plane, for example, multiple such gray visual targets and one adapted visual target can be shown, or conversely, multiple adapted visual targets and one such gray visual target can be shown. The test subject can be required to identify the visual target among the shown visual targets that is different from the other visual targets.

[0059] According to an embodiment, the applied optical effect is varied at least until the limiting refraction for a selected preferred direction, from which the test subject recognizes the pointing feature of the adapted visual target. Here, the size of the shown adapted visual target can remain constant. Here, the extreme values of the refractive unit used (e.g., ±20 diopters) can be used as the starting value of the applied optical effect, for example. Alternatively, a diopter value that deviates from the predetermined deviation (e.g., ±5 diopters) from the actually required optical spherical correction according to the visual defect data can also be used as the starting value. After applying the starting value, the applied optical effect is varied, for example, continuously or in fixed steps until the test subject can recognize (or can no longer recognize) the pointing feature of the adapted visual target. The optical effect currently applied when recognizing the pointing feature of the adapted visual target corresponds to the limiting refraction as the optical correction, wherein the test subject has a visual acuity depending on the size of the pointing feature of the shown adapted visual target. Thus, the visual acuity - refraction value pair is determined as the visual sharpness characteristic of the preferred direction.

[0060] If this method is repeated with at least one adapted second visual target, wherein the size of the pointing feature is different, then a second visual acuity - refraction value pair different from the first - determined visual acuity - refraction value pair can be determined. From these two different visual acuity - refraction value pairs, the sensitivity of the test subject can be determined, for example.

[0061] In an alternative embodiment, the size of the pointing feature of the adapted visual target is varied at least until a limiting size, up to which the test subject can recognize the pointing feature of the adapted visual target. Here, the applied optical effect can remain constant. As the optical effect, for example, an optical correction can be applied, which corrects the visual defect of the test subject in the selected preferred direction according to the visual defect data. Here, for example, the best optical correction determined within the range of objective and / or subjective refraction can be used. In this alternative, the size of the pointing feature of the adapted visual target can be changed, and the limiting size up to which the test subject can still recognize the pointing feature can be checked. According to this limiting size, the visual acuity can be determined in a conventional manner. The change in the size of the pointing feature of the adapted visual target can be achieved by showing adapted visual targets of different sizes and / or by changing the size of one or more of the shown adapted visual targets. This can be achieved within the scope of at least one visual task and / or a sequence of different visual tasks, wherein within the scope of each visual task, at least one adapted visual target is shown. Thus, in the applied optical effect, the visual acuity can be determined as the visual sharpness characteristic for the selected preferred direction. Here, the visual acuity - refraction value pair with the associated preferred direction can also be determined.

[0062] If this method is repeated with at least one second optical effect applied in the selected preferred direction, then a second visual acuity-refraction value pair different from the first determined visual acuity-refraction value pair can be determined. From these two different visual acuity-refraction value pairs, for example, the sensitivity of the test subject can be determined.

[0063] According to an embodiment, generally at least one visual acuity and / or at least one sensitivity and / or at least one visual acuity-refraction value pair and / or at least one refraction value can be determined as visual sharpness characteristics. Herein, in particular, values related to visual acuity can be determined, that is, at least one visual acuity and / or at least one sensitivity and / or at least one visual acuity-refraction value pair.

[0064] Herein, the sensitivity can be determined according to a sensitivity metric, for example, especially at least for the selected preferred direction. Additionally, the sensitivity can also be determined for a second preferred direction, that is, a direction rotated 90° relative to the selected first preferred direction. However, it is also possible (alternatively or additionally) to determine a direction-independent sensitivity. For example, the direction-independent sensitivity can be determined according to the sensitivities of the first and second preferred directions or based on two direction-independent visual acuity-refraction value pairs (wherein, for example, the relevant direction-independent visual acuity has been determined as the average of the visual acuity values of the two preferred directions) or based on a sensitivity metric that can determine the direction-independent sensitivity from at least two direction-dependent visual acuity-refraction value pairs.

[0065] According to an embodiment, at least one visual task depending on the shown adapted visual target is provided to the test subject, and the test subject responds to the visual task with active and / or passive feedback. Embodiments of active feedback can be, for example, that the test subject verbally responds to questions of the optometrist and / or another examiner regarding the visual task. Similarly, active feedback can be given, for example, by manipulating buttons and / or a mouse, using gestures and / or eye gaze. Herein, for example, the eye gaze of the test subject can be detected by means of an eye tracking unit.

[0066] With this eye tracking unit, passive responses, i.e., passive feedback, can also be given. Thus, it is possible to identify the visual target that the test subject is just looking at with the eye tracking unit. Here, it can be identified whether the test subject is, for example, subconsciously looking at a visual target different from other visual targets because it recognizes it, or whether the test subject cannot recognize the different visual target. In principle, visual tasks with passive and active responses can be combined with each other. Preferably, the response of the test subject, i.e., the feedback, is detected without the intervention of the examiner. Thus, the test subject can preferably actively input the feedback itself, for example, by means of a button and / or a mouse-like controller, or it is detected passively. Omitting the examiner (as the necessary recipient of the visual task), i.e., the human examiner, eliminates possible error sources in the determination of visual acuity. In addition, costs and / or time can be saved by omitting the human examiner.

[0067] According to an embodiment, the visual acuity of the test subject in a selected preferred direction is determined in two different applied optical effects, and thus the sensitivity of the test subject is determined. For example, the visual acuity in the selected preferred direction can be determined once using the best and / or optimal optical effect for the selected preferred direction, and the visual acuity can be determined another time using a different applied optical effect. This additional optical effect may, for example, be shifted by ±0.5 dpt relative to the optimal effect. The sensitivity of the test subject can be determined from two visual acuity values generated for the test subject in two different optical effects (i.e., corrections).

[0068] In principle, the sensitivity can also be determined based on two visual acuity values that are not both determined in the optimal correction. With the aid of a mathematical model, the sensitivity of the eye and / or the test subject can be calculated based on the two determined visual acuity values. Thus, it is not necessarily required here that the optimal correction is already known at the time of the determination of visual acuity.

[0069] Not all correction values and / or visual acuity values for measuring sensitivity have to be detected using the method according to the invention. Thus, for example, at a given distance from the refraction objectively determined here, a first visual acuity can be determined, for example, within the scope of an autorefraction measurement and / or an aberration measurement, and a second visual acuity can be determined, for example, within the scope of a subsequent subjective refraction in the optimal optical correction produced by the subjective refraction.

[0070] However, the method according to the present invention can also be used to detect two or more visual acuity values. In the scope of autorefraction and / or aberration measurement, for example, a first visual acuity value can be determined, for example, in the objectively determined best correction here, and a second visual acuity can be determined at a given distance therefrom. To calculate the actual visual acuity of the test subject, the objectively determined refractive error here can be used as the best optical correction.

[0071] According to an embodiment, subjective and / or objective refraction is performed, and the visual defect data of the test subject is derived from the visual defect determined here for the test subject. Thus, the visual defect data can be determined from the objective refraction, where the determined best optical correction and the determined best axis position are used as the visual defect data. Alternatively or additionally, subjective refraction can be performed. Here, the visual defect data can be based on the result of the subjective refraction. Finally, the two results can also be combined, and the average value of the objectively determined best correction and the subjectively determined best correction can be used as the visual defect data. Especially in the scope of sensitivity determination, an optical correction deviating from the determined best correction can also be used as the visual defect data.

[0072] In an embodiment, for example, an objective refraction measurement is first performed on the test subject, and the best optical correction determined here is used as the visual defect data. Subsequently, subjective refraction is performed, where two visual acuity values are determined using the method according to the present invention during the subjective refraction. The sensitivity is determined based on these two visual acuity values. Here, in particular, after the subjective refraction, the visual acuity value is determined based on the visual defect data generated from the subjectively determined best optical correction. In this embodiment, objective refraction and subjective refraction are performed, the visual acuity of the test subject is determined, and its sensitivity is determined. Only spherical optical correction is applied here to determine the visual acuity. No optical cylindrical correction is required.

[0073] According to an embodiment, the visual acuity of the test subject is determined as a visual sharpness characteristic by means of a method and converted into a different type of visual acuity. This conversion can be performed afterwards. Visual acuity usually depends on the visual target used. Since there are different methods to determine visual acuity, for example, based on numbers or by means of gratings, such as FrACT, the visual acuity value may depend on the determination method used. Visual acuity values depending on the measurement method can be converted into each other. The conversion can be achieved by performing a calibration function for the desired conversion.

[0074] The calibration function can be determined by regression from a data set that contains multiple visual acuity values and thus contains types of visual acuity obtained for the same person by different measurement methods (e.g., based on numbers and FrACT). Thus, a correlation between two different types of visual acuity and / or visual acuity values can be established through the data set. In the simplest case, the calibration function can here be a function of the visual acuity determined by this method, and the visual acuity value resulting from other desired determination methods is calculated as the function value.

[0075] To improve the conversion accuracy, the calibration function may depend on additional parameters, such as the pupil diameter present in the person before the visual acuity measurement, the orientation of the selected preferred direction, the adapted optotype used, the uncorrected optical effect in one or two principal meridians (e.g., in the best corrected or strongest uncorrected principal meridian), additional parameters of the adapted optotype used (e.g., its contrast), or a combination of some or all of these parameters. What the use of the calibration function enables is to convert the visual acuity value obtained by this method into a visual acuity value calculated by other methods, e.g., by using an optotype for refraction without orientation features.

[0076] According to an embodiment, at least one adapted optotype is shown clearly for the test subject without correction and / or without full correction of the optical cylinder correction required by the test subject. Here, although the correction of the astigmatic visual defect is absent or incomplete, an image element that appears clear can still be shown to the test subject. For this purpose, at least one image element is shown as an adapted optotype that is aligned with the preferred direction and is thus perceived as clear by the test subject. This is achieved without and / or without full correction of the optical cylinder correction required by the test subject. By showing at least one orientation feature of the adapted optotype oriented parallel to the preferred direction, the test subject can feel that it is clear. Thus, despite the lack of (full) cylinder correction, the adapted optotype can still be perceived as clear and can be fixated better and / or more simply by the test subject compared to an optotype shown as blurred. This can be advantageous, for example, when measuring the adaptation ability, because a test subject with uncorrected astigmatism will perceive the observed object becoming blurred more quickly.

[0077] If, for example, an image of a hot air balloon is used as the target of a visual task, then the direction in which the stripes on the hot air balloon extend (also see for this Figure 6 and Figure 7) can be shown to be arranged parallel or perpendicular to the selected preferred direction. Even without cylindrical correction, the test subject can clearly perceive the image of the hot air balloon with stripes having such an orientation as a pointing feature and thus perceive it faster. Here, the stripe pattern of the hot air balloon can be shown like a shadow to adapt to the selected preferred direction.

[0078] What can be achieved thereby is to set the visual task with sufficient precision, for example when determining the refractive value and / or the visual acuity value without correcting the astigmatism of the test subject (or in the case of incompletely corrected astigmatism).

[0079] One aspect relates to the use of an adapted visual target, each of the adapted visual targets having a pointing feature arranged parallel to a preferred direction, which preferred direction either corresponds to the axis position assigned to the optical cylindrical correction required for the test subject or is rotated 90° relative to this axis position, or the preferred direction can be derived from the wavefront data by means of a point spread function, in order to determine the visual acuity characteristics of the test subject for the selected preferred direction taking into account at least one dimension of the pointing feature of the adapted visual target.

[0080] Within the scope of the above-described method, the use of the adapted visual target can in particular be achieved. Thus, for all embodiments of the method, the use can also be involved, and vice versa.

[0081] One aspect relates to a device for determining the visual acuity characteristics of a test subject having at least one astigmatic visual defect. The device has a selection module for selecting a preferred direction, where the preferred direction either corresponds to the axis position assigned to the optical cylindrical correction required for the test subject or is rotated 90° relative to this axis position. Alternatively, the preferred direction can be derived from the wavefront data by means of a point spread function. The refractive unit is configured to apply an optical effect to the test subject at least in the selected preferred direction. The refractive unit can for example be configured as an aberrometer and / or an optometer and / or apply a rotationally symmetric lens as spherical correction, as the optical effect. The display module has a display and shows at least one adapted visual target having a pointing feature on the display such that the pointing feature of the adapted visual target is arranged parallel to the preferred direction. The visual acuity characteristics determination module determines the visual acuity characteristics of the test subject for the selected preferred direction taking into account at least one dimension of the pointing feature of the adapted visual target and the applied optical effect.

[0082] The device can for example be used to carry out the above-described method and / or use the above-described adapted visual target. Thus, all embodiments of the device are also related to the method and the use, and vice versa.

[0083] As a dimension of the pointing feature, for example, the distance between the hatching lines, the contrast intensity, the thickness of the line and / or the width of the notch can be used.

[0084] According to an embodiment, the device has an eye tracking unit that tracks at least one eye of a test subject when showing at least one adapted visual target. Through the eye tracking unit, on the one hand, the line-of-sight direction of the test subject can be determined, and on the other hand, the active and / or passive feedback of the test subject can be recorded as a response to a visual task.

[0085] Within the scope of the present invention, the terms "substantially" and / or "about" may be used such that they include a deviation of up to 5% from the value following the term, a deviation of up to 5° from the direction following the term, and / or an angle following the term.

[0086] Terms such as above, below, over, under, lateral, etc. relate to the earth reference system in the operating position of the subject matter of the present invention, unless otherwise stated. Description of the Drawings

[0087] The present invention will be described in detail hereinafter with reference to the embodiments shown in the drawings. Herein, the same or similar reference numerals may represent the same or similar features of the embodiments. Each feature shown in the drawings may be implemented in other embodiments. Among them:

[0088] Figure 1A An embodiment of the shown visual target for determining visual acuity is shown;

[0089] Figure 1B The visual impression generated by the test subject for the Figure 1A shown visual target is shown, and the test subject is corrected for its second principal meridian of the cylindrical vision defect using optical spherical correction;

[0090] Figure 1C The visual impression generated by the test subject for the Figure 1A shown visual target is shown, and the test subject is corrected for its first principal meridian of the cylindrical vision defect using optical spherical correction;

[0091] Figure 2A An embodiment of an adapted visual target for the visual task of the test subject is shown, and the test subject is corrected for its second principal meridian of the cylindrical vision defect using optical spherical correction;

[0092] Figure 2B The visual impression generated by the test subject for the Figure 2A shown visual target is shown, and the test subject is corrected for its second principal meridian of the cylindrical vision defect using optical spherical correction;

[0093] Figure 3AShows an embodiment of an adapted visual target for a visual task of a test subject, which is corrected by optical spherical correction for the second principal meridian of its cylindrical visual acuity defect;

[0094] Figure 3B Shows the visual impression produced on a test subject for Figure 3A the visual target shown, which is corrected by optical spherical correction for the second principal meridian of its cylindrical visual acuity defect;

[0095] Figure 4A Shows the visual impressions produced on a test subject of an adapted visual target for visual targets of different sizes, wherein the test subject is corrected by optical spherical correction for the second principal meridian of its cylindrical visual acuity defect;

[0096] Figure 4B Shows the visual impressions produced on a test subject of an adapted visual target for visual targets of different sizes, wherein the test subject is corrected by optical spherical correction for the second principal meridian of its cylindrical visual acuity defect;

[0097] Figure 5A Shows an embodiment of an adapted visual target for a visual task of a test subject, which is corrected by optical spherical correction for the second principal meridian of its cylindrical visual acuity defect;

[0098] Figure 5B Shows the visual impression produced on a test subject for Figure 5A the visual target shown, which is corrected by optical spherical correction for the second principal meridian of its cylindrical visual acuity defect;

[0099] Figure 6 Shows an exemplary image or photograph that conveys a sense of distance to an observer;

[0100] Figure 7 Shows Figure 6 an image or photograph of, which has an exemplary adapted visual target integrated in or superimposed on the image; and

[0101] Figure 8 Shows a graph (Duane curve) of the accommodation amplitude versus age. Detailed Description

[0102] The drawings show embodiments of a test chart and the resulting visual impression in the case of a test subject with an astigmatic visual defect. The following test subject is assumed, which has a visual defect of +2.75 dpt in the spherical lens and for this purpose has an astigmatism of -3.0 dpt at an axis position of 12°. The visual defect data should be understood by way of example, and the subsequent embodiments can generally be transferred to a test subject having a visual defect in the spherical lens s and for this purpose having an astigmatism z at an axis position α.

[0103] The visual defect of the test subject can be detected within the scope of subjective and / or objective refraction. This results in visual defect data, which contains spherical and astigmatic visual defects as well as the axis position, i.e., for example, at least contains the value set {s; z; α}, and in this example contains the value set {+2.75 dpt; -3.0 dpt; 12°}.

[0104] Figure 1A Embodiments of test charts that can be shown to the test subject to determine their visual acuity are shown. Landolt rings are used as the test chart, and the notches are shown oriented at angles of 180°, 135°, 90°, 45°, and 0° from left to right, respectively. The five Landolt rings on the left are common standard test charts, which can also be used, for example, within the scope of conventional visual acuity determination.

[0105] On Figure 1A the right side of, two special and adapted test charts are also shown, in which the notches are shown oriented at angles of 168° and 78°.

[0106] When determining their visual acuity as a visual sharpness characteristic, an optical correction is applied and / or provided to the test subject as an optical effect. The test subject observes the test chart through the optical correction and can attempt to recognize the test chart. For this purpose, a refractive unit, for example, arranged in front of the test subject's eyes can be used.

[0107] Here, for example, a refractive unit can be used through which only (can) an optical spherical correction is applied to the test subject, but not necessarily also an optical cylindrical correction. Therefore, a refractive unit with only spherical correction can be used, or a refractive unit with only a limited selection of axis positions and / or optical cylindrical correction can be applied.

[0108] To determine the visual sharpness characteristic of the test subject, a preferred direction is now first selected from the visual defect data. The preferred direction is a direction in a plane arranged approximately perpendicular to the line of sight direction of the test subject. The preferred direction can be arranged in the same plane in which the axis position of the cylindrical visual defect of the test subject is also defined.

[0109] Now, as a preferred direction, the axial position α and thus the first principal meridian of the cylindrical visual defect of the test object can be selected, or the direction α + 90° perpendicular thereto in the same plane and thus the second principal meridian of the cylindrical visual defect of the test object can be selected. In this example, this is the 12° direction in the plane approximately perpendicular to the line of sight direction of the test object as the first preferred direction of the first principal meridian, and the 102° direction in the plane approximately perpendicular to the line of sight direction of the test object as the second preferred direction of the second principal meridian.

[0110] If the first preferred direction is selected, then an optical spherical correction of s (in the example +2.75 dpt) can be applied to the test object by the refractive unit. Thereby, its visual defect is correctly corrected in the first preferred direction, but not in other directions, especially not perpendicular to the first preferred direction.

[0111] If the second preferred direction is selected, then an optical spherical correction of s + z can be applied to the test object by the refractive unit, which is -0.25 dpt in the example (calculated from +2.75 dpt - 3.0 dps). Thereby, its visual defect is correctly corrected in the second preferred direction, but not in other directions, especially not perpendicular to the second preferred direction.

[0112] Thus, if, for example, an optical spherical correction of -0.25 dpt is applied to the test object, then its visual defect is relatively precisely corrected in the second preferred direction V2 at 102°. Figure 1B The leftmost shows this correction schematically. Since the axial position of the visual defect is usually determined when observing the eye of the test object, and the test chart is usually shown by observing the test object, the measurement angle of the axial position is exactly mirror-inverted with respect to the display angle of the test chart. This means that the second preferred direction V2 is oriented at a display angle of 78° on the display showing the test chart, which corresponds to the axial position at a measurement angle of 102° when observing the eye of the test object.

[0113] For example, a display angle pointing vertically upward (corresponding to "12 o'clock") corresponds to the 90° position. The measurement angle pointing vertically upward (corresponding to "12 o'clock") on the display plane also corresponds to 90°.

[0114] The rightward-pointing display angle at "3 o'clock" corresponds to 0°. However, the rightward-pointing display angle corresponds to the measurement angle rotated leftward (due to mirror inversion) when observing the display plane, i.e., the measurement angle of 180°.

[0115] Therefore, there is a difference in the angle values between the display angle defined on the display plane of the display and the measurement angle measured when observing the eye of the test object.

[0116] Figure 1B shows the visual impression of the test subject when observing Figure 1A the shown optotype. Here, the optotype appears blurred especially in a direction perpendicular to the second preferred direction V2. Figure 1B The shown visual impression is determined computationally for the test subject according to this example using the refractive error data {s = +2.75 dpt; z = -3.0 dpt; α = 12°}.

[0117] As Figure 1B shown, optotypes with notches shown at display angles of 90° and 45° appear very blurred especially for the test subject.

[0118] Now, the test subject uses specially adapted optotypes, where the notches are oriented perpendicular to the second preferred direction V2, i.e., at display angles of 168° and 348°. Figure 1A Also shown is an adapted Landolt ring at a display angle of 168° as the actually shown adapted optotype. In these two adapted optotypes, the pointing feature of the Landolt ring is oriented precisely parallel to the second preferred direction V2, i.e., transitioning from the black circular edge to the white notch and back to the black circular edge. Thus, the notches of the two adapted Landolt rings "rotated" to display angles of 168° and 348° appear relatively clear at least for the test subject, see Figure 1B the two right - hand visual impressions in. This is because with an optical spherical correction of - 0.25 dpt maintained, the refractive error of the test subject in its second principal meridian, i.e., along the second preferred direction V2, is corrected quite well and / or optimally.

[0119] The pointing feature of the Landolt ring (whose notches are shown at display angles of 90° and 45°) is relatively steep (i.e., almost perpendicular) to the corrected second preferred direction V2, and thus a very blurred visual impression is produced especially for these two optotypes. However, a blurred visual impression is also produced for other standard optotypes, and this does not allow for an accurate determination of visual acuity.

[0120] If an optical spherical correction of +2.75 dpt is applied to the test subject, then its refractive error is corrected relatively accurately or optimally in the first preferred direction V1 at a measurement angle of 12°. This correction is shown Figure 1C at the far left. The axis position at a measurement angle of 12° appears on the display, in the display plane, at a display angle of 168°. Thus, the first preferred direction V1 is oriented on the display at a display angle of 168°.

[0121] Figure 1C shows the visual impression of the test subject when observing Figure 1AThe visual impression when the presented optotype is viewed. Here, the optotype appears blurred especially in a direction perpendicular to the first preferred direction V1. Figure 1C The presented visual impression is determined computationally for the test subject according to this example using the refractive error data {s = +2.75 dpt; z = -3.0 dpt; α = 12°}.

[0122] As Figure 1C shown, standard optotypes with notches shown at display angles of 180°, 135°, and 0° appear very blurred especially for the test subject.

[0123] Now, the test subject can again use specially adapted optotypes, where the notches are oriented perpendicular to the first preferred direction V1, i.e., at display angles of 258° and 78°. Figure 1A Also shown is an adapted Landolt ring at a display angle of 78° as the actually presented adapted optotype. In the two adapted optotypes, the orientation characteristic of the Landolt ring is oriented exactly parallel to the first preferred direction V1, i.e., transitioning from the black circular edge to the white notch and then back to the black circular edge. Thus, the notches of the two adapted Landolt rings rotated to display angles of 258° and 78° appear relatively sharp at least for the test subject, see Figure 1C the two visual impressions on the right in. This is also because with the optical spherical correction of +2.75 dpt maintained, the refractive error of the test subject in its first principal meridian, i.e., along the first preferred direction V1, is corrected quite well and / or optimally.

[0124] The orientation characteristic of the Landolt ring (whose notches are shown at display angles of 180°, 135°, and 0°) is relatively steep (i.e., almost perpendicular) to the corrected first preferred direction V1, and thus a very blurred visual impression is produced especially for these three optotypes.

[0125] Within the scope of the visual task for determining visual acuity, it is now possible to ask the test subject, who is corrected with an optical spherical correction of -0.25 dpt in its second preferred direction V2, where the notches of the two optotypes shown at display angles of 168° and 348° point, e.g., whether they point to the left or to the right.

[0126] Alternatively or additionally, within the scope of another visual task for determining visual acuity, it is possible to query the test subject, who is corrected with an optical spherical correction of +2.75 dpt in its first preferred direction V1, where the notches of the two optotypes shown at display angles of 258° and 78° point, e.g., whether they point up or down.

[0127] Thus, it can be checked whether the test subject can still recognize the details of the pointing feature as an adapted visual target. The visual acuity for the selected preferred directions V1 and / or V2 can be determined based on the level of detail that the test subject can just still recognize.

[0128] For the calculation of the resulting visual impression shown in Figure 1B and Figure 1C and in the subsequent figures, it is assumed that the pupil diameter of the test subject is 3.0 mm, the wavelength is 550 nm, and the distance to the display is 5 m. Furthermore, it is assumed that the visual target is shown as a rendered image with 1024 x 1024 pixels, where the side length of the image is 204.8 mm and the side length of the pixel corresponds to 40 μrad = 0.1375 arc minutes.

[0129] Snellen-E also belongs to the same category of adapted visual targets as the Landolt ring. Here, the relevant feature, i.e., the pointing feature of Snellen-E, is the following sequence:

[0130] - The dark area of the outer horizontal line,

[0131] - The bright area of the background,

[0132] - The dark area of the central horizontal line,

[0133] - The bright area of the background, and

[0134] - The dark area of the other outer horizontal line.

[0135] If necessary, the bright background above and / or below can also form part of the sequence. Thus, when using Snellen-Es, the longitudinal lines connecting the horizontal lines must be oriented parallel to the selected and corrected preferred direction V1 or V2, which, as in the case of the Landolt ring, only allows two different orientations.

[0136] Figure 2A Shows additional adapted visual targets for a test subject with a vision defect with exemplary use. As adapted visual targets, squares shaded with continuous lines and without edges are used, which are shown on the display. Here, the shading lines of the first, third, and fourth visual targets on the left are oriented parallel to a display angle of 78°, while the shading lines of the second visual target on the left are oriented parallel to a display angle of 168°.

[0137] The shading lines of each visual target have the same thickness and the same orientation. Two adjacent shading lines always have the same and constant distance from each other.

[0138] The shading lines provide the pointing feature of the adapted visual target. The direction of the pointing feature is the direction in which the bright and dark areas alternate, i.e., perpendicular to the shading lines.

[0139] If the test subject is corrected for its second preferred direction V2 by applying a pure spherical optical correction of -0.25 dpt, then there is generated for the test subject Figure 2B the visual impression shown. The first, third, and fourth visual targets on the left appear as gray dots, while the shadow of the second visual target can be recognized by the test subject.

[0140] Thus, within the scope of the visual task for determining visual acuity, the test subject can recognize the adapted visual target that is different from the other visual targets. In this example, this visual target is the second visual target on the left, whose pointing feature is oriented parallel to the selected and corrected second preferred direction V2, i.e., a display angle of 78° corresponds to a measured angle of 102°, i.e., the second principal meridian of the test subject's cylindrical visual defect.

[0141] Here, the distance between two adjacent shadow lines and / or the thickness of the black shadow lines can be used as the size of the recognized details for determining visual acuity.

[0142] Figure 3A Additional visual targets of a test subject with a visual defect of exemplary use are shown. As visual targets, squares that are shaded with continuous lines and have no edges are used again, and these squares are shown on the display. Here, the shadow lines of the first, third, and fourth visual targets on the left are oriented parallel to a display angle of 315°, while the shadow lines of the second visual target on the left are oriented parallel to a display angle of 135°.

[0143] Here, the size of the squares and the distance and thickness of the shadow lines can correspond to Figure 2A the visual targets shown. Similarly, the second visual target on the left is different from the other visual targets.

[0144] If the test subject is corrected for its second preferred direction V2 by applying a pure spherical optical correction of -0.25 dpt, then there is generated for the test subject Figure 3B the visual impression shown. Since in the display angle of 78°, none of the visual targets is well adapted to the corrected second preferred direction V2, the test subject cannot recognize the individual shadows of the visual targets, because for the test subject, a visual impression of gray dots or blurred squares is generated in each of the four visual targets.

[0145] Therefore, this visual impression is significantly different from the visual impression generated in the adapted visual targets optimized for the test subject, see Figure 2A and 2B .

[0146] Figure 4AShows the visual impression of a test object when corrected for its second preferred direction V2 at a display angle of 78° by applying a pure spherical optical correction of -0.25 dpt. Here, four edge-free shaded squares are shown as visual targets, and their hatching lines are shown parallel to a display angle of 168°. Thus, the pointing features of these visual targets are oriented parallel to the corrected second preferred direction V2, and the test object can at least recognize the shading of some of the adapted visual targets, for example, the two right-hand adapted visual targets.

[0147] However, the hatching lines of the visual targets have different widths and different distances. The leftmost visual target has a distance of logMAR -0.66 between two black hatching lines, the second leftmost visual target has a distance of -0.26, the third leftmost visual target has a distance of 0.14, and the fourth leftmost visual target has a distance of 0.54. This distance can be used as a measure of visual acuity. Thus, if the test object only recognizes the two right-hand visual targets, and the visual target with the denser shading (i.e., the third from the left) has a distance of logMAR 0.14, then the smallest detail that is also recognized can be used for visual acuity determination.

[0148] Figure 4B Shows the visual impression of a test object when again corrected for its second preferred direction V2 at a display angle of 78° by applying a pure spherical optical correction of -0.25 dpt. Here again, four edge-free shaded squares are shown as visual targets, and their hatching lines Figure 4A have different widths and different distances as shown. From left to right, the visual targets have distances of logMAR -0.66; -0.26; 0.14 and 0.54 between two adjacent black hatching lines exactly as in Figure 4A .

[0149] The hatching lines are shown parallel to a display angle of 78°, so they appear most blurred to the test object; because the pointing features of the visual targets are oriented perpendicular to the corrected second preferred direction V2 here. Thus, the visual targets used in Figure 4B can at most be used as visual targets that appear grey, but not as adapted visual targets that are recognizable to the test object thus corrected.

[0150] Figure 5AShows additional optotypes for a test subject with a visual defect for exemplary use. As optotypes, squares shaded with continuous lines and without edges are used, and these squares are shown on the display. Here, the hatching lines of all optotypes are oriented parallel to a display angle of 168°. However, only half of the squares are provided with the hatching lines here. In the first and third optotypes on the left, the upper halves are respectively shaded, and in the second and fourth optotypes on the left, the lower halves are respectively shaded. The corresponding other halves are filled gray in the first and second optotypes on the left and are provided with (shortened) hatching lines perpendicular thereto, i.e., parallel to a display angle of 78°, in the third and fourth optotypes on the left.

[0151] The hatching lines provide a pointing feature for the adapted optotypes. The direction of the pointing feature is the direction in which light and dark areas alternate, i.e., the direction perpendicular to the hatching lines.

[0152] If the test subject is corrected again for its second preferred direction V2 by applying a pure spherical optical correction of -0.25 dpt, then the following visual impression is produced for the test subject. Figure 5B In the first and third optotypes on the left, the shading appears in the upper half, and in the other two optotypes, the shading appears in the lower half.

[0153] The corresponding other half of each optotype appears as gray dots. Here, for the test subject, there is actually little difference between the other half being filled with a medium gray value or being filled with hatching lines parallel to the selected second preferred direction.

[0154] Therefore, within the scope of the visual task for determining visual acuity, the test subject can be required to distinguish the shown adapted optotypes according to their visual acuity.

[0155] Here, surfaces with different fillings, especially optotypes that are only filled with hatching in a part of the adapted optotype, can also be used.

[0156] Here, the distance between two adjacent hatching lines and / or the thickness of the black hatching lines can again be used as the size of the recognized details for determining visual acuity.

[0157] As an alternative to the shaded squares shown in the drawings, all types of filled and shaded figures, such as circles, rectangles, symbols, animals, letters, etc., can be used as adapted optotypes. Preferably, they have no boundary lines that may affect the visual impression of the shading.

[0158] Here, the hatching can be perpendicular to the selected and corrected preferred direction V1 or V2, since the pointing features and associated features are the alternation of the bright and dark areas of the hatching. Here, it is advantageous for the method that the figure, such as a circle or a square, has as few details as possible. Here, for adapting the orientation, the entire target (including the hatching) can be rotated or only the hatching within the target can be rotated. Here, the hatching can be constructed binary, i.e., with hard black edges, or continuously, i.e., with a sinusoidal intensity curve, for example.

[0159] Visual task

[0160] For determining visual acuity, a visual task showing the adapted target can be provided to the test subject. In the visual task, a distinction can be made between visual tasks with active and passive feedback of the test subject. Here, active feedback can be understood as statements output by the test subject, for example, verbally or by consciously observing the target and detecting the line-of-sight direction by means of eye tracking. Passive feedback can be understood as the tracking of the presented moving target. Here, it can be inferred whether the target is still safely recognized by means of the line-of-sight movement detected by the eye tracking unit.

[0161] The target is shown and thus presented to the test subject in a defined presentation type. Here, the presentation type is understood as properties such as contrast, size, or hatching frequency. Here, the size is a particularly important property for this type of target, such as the Landolt ring and Snellen-E, which can be shown in two ways mirror-inverted with respect to the selected preferred direction. The hatching frequency is a very important property for this type of target with a shaded surface and / or consisting of shaded surfaces.

[0162] The presentation type can deteriorate in such a way that the presentation type is changed to a worse recognizability, for example, by reducing the size (especially in the case of the adapted target that can be shown in two ways mirror-inverted with respect to the selected preferred direction), reducing the contrast, and / or increasing the hatching frequency (especially in the case of the adapted target with a shaded surface and / or consisting of shaded surfaces).

[0163] In an embodiment of the visual task with active feedback, one or more adapted targets that can be shown in two ways mirror-inverted with respect to the selected preferred direction are presented. In these shown targets, the orientation of the target should be recognized by the test subject.

[0164] Showing multiple targets of the same presentation type allows for a more reliable judgment of the answer. Here, the deterioration of the presentation type until the point where the target can no longer be recognized allows for the determination of visual acuity.

[0165] In an embodiment of a visual task with active feedback, one or more adapted visual targets of this type with a shaded side and / or consisting of a shaded side are presented. The test subject is required to recognize the presence of the shadow of the visual target.

[0166] Showing multiple visual targets of the same presentation type allows for a more reliable judgment of the answer. Here, the deterioration of the presentation type until the point where the presence of the visual target or the shadow can no longer be recognized allows for the determination of visual acuity.

[0167] In addition, one or more adapted visual targets with an adapted orientation and one or more adapted visual targets with an orientation different therefrom, for example, an orientation orthogonal thereto, can also be presented. In a visual target of this type with a shaded side and / or consisting of a shaded side, the visual target can be presented using a uniform fill, and the test subject can be asked whether they can recognize the difference and / or which one or more visual targets are different from the other visual targets. This type of visual task is also referred to as "forced choice".

[0168] In an embodiment of a visual task with passive feedback, one or more adapted moving visual targets of one of the previously mentioned types are presented. Here, the presentation type can deteriorate continuously and / or gradually. By means of the line-of-sight movement detected by an eye-tracking unit, it is possible to infer the presentation conditions for reliably recognizing the visual target and / or visual object. From this, the visual acuity of the test subject can be derived and / or determined.

[0169] The visual target can be shown by a light field display. Here, the applied optical spherical correction does not have to be applied physically, but the optical spherical correction can be simulated as a wavefront.

[0170] Combination with eye tracking

[0171] In a visual task with active feedback, eye tracking allows for the automation of the constitution. In a visual task with passive feedback, eye tracking may be absolutely necessary.

[0172] In an embodiment, when solving a visual task by means of at least one image and / or video of the pupil and / or one or more Purkinje reflections, the line-of-sight direction of the test subject can be determined. The line-of-sight direction can also be determined by a combination, for example, determined by the Purkinje reflection obtained in the pupil video. For this purpose, the device for determining visual acuity can have at least one calibrated image recording device, such as a digital camera.

[0173] In an embodiment, the eye tracking unit is used to position the optical unit, i.e., for centering and / or focusing the optical unit. Here, the measuring head of the device can be centered and / or focused, for example. Subsequently, this positioning can be kept constant, and the eye tracking unit can be used to determine the line of sight direction of the test subject, for example for passive and / or active responses to visual tasks. Here, different tasks can be solved using only one eye tracking unit.

[0174] Integrated into an optometric measuring device

[0175] The determination of visual acuity can be combined with the determination of visual defects, in particular for determining visual defects according to sphere, cylinder and axis. Here, lower-order and possibly higher-order aberrations can also be determined.

[0176] For this purpose, the device for determining visual acuity is connected and / or combined with an autorefractor or aberrometer unit.

[0177] In an embodiment, it is here assumed that an autorefractor and / or aberrometer serves as a refractive unit, which has a display unit and an optical unit for presenting an adapted visual target and thus a target. If necessary, this unit can also be used for defocus to determine visual acuity without the need for additional optical components.

[0178] Ideally, the display unit is here configured as a programmable display in order to be able to present diagrams adapted to different tasks. Alternatively, however, the visual target display can also be used for defocus in autorefraction and / or aberrometry. By means of a beam splitter and / or mechanical means, switching between the displays can be effected.

[0179] What this device allows is to first determine the visual defect with the aid of an autorefractor and / or aberrometer, and to derive visual defect data from the result of this measurement, and thus to derive a preferred direction with the effect applied for this preferred direction.

[0180] In such a device, the existing eye tracking unit for centering and / or focusing autorefraction and / or aberrometry can be used to track the line of sight direction of the test subject.

[0181] In this device, within the scope of autorefraction and / or aberrometry, the same unit can be used to present at least one visual target and thus a target and, if necessary, to present defocus. For autorefraction and / or aberrometry, it may be sufficient or even meaningful to use a relatively small visual target as the target, since it pre-adjusts the line of sight of the test subject before fine adjustment is caused by observing an excellent visual target.

[0182] In a blurred state, small visual targets can be used as targets and / or can be advantageous because (if the test subject does not recognize any details) the small bright spot of a small target better controls the line of sight than an enlarged bright spot.

[0183] Conversely, larger visual targets can generally help to determine visual acuity as a target because it allows the presentation of multiple different visual targets and especially allows larger eye movements in visual tasks that detect eye movement. This can be achieved using a sub-device that allows the convergence and / or divergence of the light of the presented target, i.e., the "optical distance", and the size of the image of the presented target. This can be achieved, for example, by combining a display with two axially movable spherical lenses, where the axial distance between the two lenses can be adjusted independently of the display.

[0184] Additionally or alternatively, one or more other measurement units can be integrated here, such as an opacity unit, a topography and / or geomorphology unit, a fundus camera, and / or an intraocular pressure measurement unit. Individual components of multiple units can also be used here.

[0185] Accommodation and the influence of other principal meridians

[0186] If the exact design of the visual target and / or visual task should potentially result in accommodation and / or the influence of unobserved principal meridians, then the method can be changed as follows.

[0187] Due to accommodation, the planes in which the two principal meridians are clearly imaged are pulled forward (i.e., in the direction from the retina to the lens). Thus, in this embodiment, the posterior principal meridian (i.e., the principal meridian that is less refracted by the eye) is clearly imaged on the retina using spherical correction, and / or if blurriness (e.g., within the range of sensitivity determination) is desired, then it is imaged in front of the retina. To avoid the influence of accommodation, the direction in which the principal meridian that is less refracted by the eye is clearly imaged is selected here as the preferred direction for presenting the visual target.

[0188] According to the embodiment, the principal meridian that achieves weaker refraction in the test subject's eye is thus selected as the preferred direction. Thereby, the influence of accommodation on visual acuity determination can be reduced.

[0189] To avoid the influence of other principal meridians when determining the visual acuity of an optical spherical correction that is different from the best correction in the observed principal meridian, for example, in the case of applied blur, such as for determining sensitivity, the correction may deviate from the direction required for correction in other principal meridians.

[0190] Here, especially considering the above regarding accommodation, the observation of the principal meridian with weaker refraction and blur in the positive direction is used, which is also referred to as blurriness in the narrow sense.

[0191] Thus, in an embodiment, the principal meridian in which weaker refraction occurs in the eye of the test subject is selected as the preferred direction. To determine the sensitivity, the visual acuity value is determined in the case of applying an optical spherical correction that deviates from the sought-after optimal optical spherical correction in the positive direction. Additionally, the visual acuity value can be determined in the case of applying the sought-after optimal optical spherical correction. From these two visual acuity values, the visual acuity and its sensitivity of the test subject can be determined as accurately as possible, wherein the influence of adaptation and other principal meridians can be reduced.

[0192] Taking into account HOA

[0193] If a wavefront measurement of the eye is performed, if necessary taking into account higher-order aberrations (abbreviated as HOA), then this wavefront measurement can be used instead of objectively and / or subjectively determined refractive values in order to provide visual defect data therefrom. Thus, the preferred direction can be selected with the aid of the wavefront measurement, to which the adapted test chart is oriented. In addition, the intensity of the optical spherical correction applied to the selected preferred direction can also be derived from the wavefront measurement.

[0194] Here, the point spread function can be determined according to methods known from the literature, based on the wavefront data, the optical spherical correction (and / or spherical correction) applied when determining the visual acuity, and the pupil size. Instead of determining the preferred direction of the adapted test chart by means of subjective and / or objective refraction in (Zernike) order two, the preferred direction can be derived from the point spread function, for example from the direction and / or axis of the smallest extension of the point spread function. Here, the direction of least confusion can be selected, for example as the direction of the smallest standard deviation of the point spread function.

[0195] Determining the sensitivity

[0196] In some embodiments, the sensitivity of at least one eye of the test subject or spectacle wearer is determined. Thus, spectacle lenses for at least one eye of the test subject can be calculated, optimized or evaluated taking into account the determined sensitivity of at least one eye of the test subject. This can be used for manufacturing spectacle lenses.

[0197] In methods for optimizing spectacle lenses according to the prior art, the spectacle lenses are optimized by minimizing or maximizing an objective function that includes the actual value and the corresponding target value of at least one imaging property or aberration of the spectacle lens. At least one imaging property or aberration can represent a direct quantification of the wavefront deviation from a reference wavefront. An exemplary objective function is, for example, the following function:

[0198] F = ∑ i [G R，i (R actual (i) - R target(i)) 2 +G A，i (A actual (i)-A SPK,target (i)) 2 +...

[0199] wherein:

[0200] i (i = 1 to N) represents the evaluation points of the spectacle lens;

[0201] R actual (i) represents the actual spherical effect or refractive error at the i-th evaluation point;

[0202] R actual (i) represents the target spherical effect or target refractive error at the i-th evaluation point;

[0203] Ast actual (i) represents the astigmatism or astigmatism error at the i-th evaluation point;

[0204] Ast target (i) represents the target astigmatism or target astigmatism error at the i-th evaluation point.

[0205] The parameter G R，i 、G A，i ... are the corresponding weights of the imaging characteristics or aberrations used in the optimization.

[0206] Quantifying the wavefront deviation in diopters directly without considering the effective pupil size is not the best criterion for describing and judging the perception of a spectacle wearer through the spectacle lens due to the associated depth of field. Based on this understanding, as proposed in DE 102017 007 663 A1, visual acuity (visual sharpness) is directly considered in the target or quality function. The visual acuity included in the target or quality function is related to at least one imaging characteristic or aberration assigned to the spectacle lens system, wherein at least one imaging characteristic or aberration can be evaluated on a suitable evaluation surface (e.g., on the vertex sphere or in the eye). The spectacle lens system can consist of at least one spectacle lens (e.g., the spectacle lens of a refractive spectacle). However, preferably, the spectacle lens system includes additional components, such as a model eye or eye model, which can be based on the average value of the spectacle wearer or at least one individual parameter of the spectacle wearer's eye. In other words, the spectacle lens system on which the assignment of at least one imaging characteristic or aberration to the visual acuity of the spectacle wearer is based can be a spectacle lens-eye system.

[0207] As described in DE 10 2017 007 663 A1, by at least one imaging characteristic or aberration ΔU s，jAn exemplary objective or quality function associated with the visual acuity V of a spectacle wearer or a normal spectacle wearer may have the following structure, for example:

[0208]

[0209] In the above formula, V(ΔU s，j (i)) represents a function that describes the correlation between visual acuity and at least one imaging characteristic or aberration of the spectacle lens system at the i-th evaluation point (i = 1, 2, 3,..., N) on the evaluation surface. In other words, V(ΔU s，j (i)) describes an exemplary association between at least one imaging characteristic or aberration of the spectacle lens system and the visual acuity of the test object or the spectacle wearer or a normal spectacle wearer when observing an object through the spectacle lens system. The independent variable ΔU s, j is general and can represent any imaging characteristic or aberration of the spectacle lens system, which describes the effect of the spectacle lens system on the light beam emitted by the object or the difference in the effect of the spectacle lens system on the light beam emitted by the object and the reference light beam converging on the retina of the eye. Here, one or more imaging characteristics or aberrations can be included in the objective or quality function and evaluated, where the subscript j, j ≥ 1 represents the j-th imaging characteristic or aberration.

[0210] V actual (ΔU s，j (i)) represents the visual acuity obtained according to the assignment and actual value of at least one imaging characteristic of the spectacle lens to be calculated (e.g., optimized) or evaluated at the i-th evaluation point, and V target (ΔU s，j (i)) represents the corresponding target value of the visual acuity.

[0211] At least one imaging characteristic or aberration can be calculated or evaluated at a suitable evaluation surface. Therefore, the subscript "s" represents any evaluation surface of at least one imaging characteristic or aberration ΔU s，j . The evaluation surface can be, for example, a plane (evaluation plane) or a curved surface (e.g., a spherical surface). The evaluation surface can be, for example, the vertex sphere or a surface in the eye, such as one of the following planes or surfaces:

[0212] A plane or (e.g., spherical) surface behind the cornea,

[0213] The front surface of the lens or a plane tangent to the front surface of the lens,

[0214] The back surface of the lens or a plane tangent to the back surface of the lens,

[0215] The plane of the exit pupil (AP); or

[0216] Plane (L2) of the rear surface of the lens.

[0217] Parameter Denotes the weight of the assigned preset visual acuity for the imaging characteristic ΔU s, at the i-th evaluation point with respect to the visual acuity of the j-th

[0218] Here, for example, one of the visual acuity models described in DE 10 2017 007 663 A1 or any other suitable visual acuity model (which in particular describes visual acuity as a function of refraction or ametropia) can be used, i.e., preferably a prescribed combination of how the visual acuity model can be incorporated into the optimization objective function in combination with the transformation of the target specification and the weight. In this case, it is noted that within the scope of this specification, preferably a sensitivity measure (described below) can be used based on such a visual acuity model (as the functional correlation between the visual acuity value and refraction / ametropia). In particular, the preferred sensitivity measure can be used as the derivative of the visual acuity model (i.e., the functional relationship between the visual acuity value and refraction / ametropia) after refraction / ametropia.

[0219] The spectacle lens can also be evaluated by means of an objective function, wherein at at least one evaluation point of the spectacle lens to be evaluated, the actual value of at least one imaging characteristic of the spectacle lens to be evaluated is calculated and compared with the corresponding target value.

[0220] As can also be seen from DE 10 2017 007 663 A1, the knowledge of the so-called sensitivity, i.e., the change of visual acuity with ametropia, first contributes to the calculation, optimization and / or manufacture of highly customized and high-quality spectacle lenses. Thus, the assignment or functional relationship V(ΔU s，j (i)) of at least one imaging characteristic or aberration of the spectacle lens system to the visual acuity of the spectacle wearer may be parametrically related to the measured output visual acuity and / or the determined sensitivity of the spectacle wearer.

[0221] Sensitivity is a (particularly phenomenological) parameter or parameter used in ophthalmic optics and ophthalmology, and the correlation between visual acuity and ametropia can be described or explained using said parameter or parameter. The sensitivity of the eye is particularly understood as the change in the visual acuity of the eye in the case of a change in ametropia. In particular, sensitivity can be defined as the derivative of visual acuity after ametropia, or as the local derivative of visual acuity in a specific ametropia after ametropia. Here, ametropia is the deviation of the effect or refraction provided for at least one eye of the test subject from the ideal refraction determined or known for at least one eye in the determination of visual acuity. The ideal refraction (hereinafter also referred to as the best refraction or target refraction) can be determined, for example, from conventional objective and / or subjective refraction measurements. Sensitivity particularly describes how much the visual acuity changes when the optical effect or correction in front of the eye changes. Sensitivity can be quantitatively described in particular by means of a sensitivity measure and / or by means of a visual acuity model.

[0222] Therefore, when calculating and / or creating customized spectacle lenses, especially when creating multifocal spectacle lenses (such as ophthalmic spectacle lenses), the sensitivity of at least one eye of the test subject can be taken into account. The spectacle lens can have a transition between regions with different optical corrections, for example, a transition between a viewing point for hyperopia and a viewing point for myopia. Specifically, these transitions between regions of the spectacle lens with different optical corrections can be designed differently. Here, for example, a hard transition or a soft transition is mentioned, depending on the intensity or smoothness of the refractive change along the transition. In the case of highly customized and high-quality spectacle lenses, this transition (but also other regions of the spectacle lens) can be adjusted in particular according to the sensitivity of at least one eye of the test subject or spectacle wearer.

[0223] To determine the sensitivity of at least one eye of the test subject to blur, the presence of at least two application effects and the visual acuities achieved thereby are required. Within the scope of the present invention, these effects can be determined as visual acuity-refraction value pairs of the visual acuity characteristic. Subsequently, the relevant models and corresponding formulas for calculating sensitivity are described. According to the prior art, a quantification effect is provided for the test subject or at least one eye of the test subject to determine sensitivity (for example, in the case of using a conventional trial lens set, in steps of 0.25 dpt). Using a visual acuity chart with visual targets of a quantified size or quantified visual acuity level, the corresponding visual acuity is determined for each provided effect. In addition, the best correction (or best refraction or target refraction) must be determined for the test subject in order to be able to convert the provided effect into ametropia.

[0224] The double quantization associated with conventional methods results in high measurement uncertainty. Conventional methods are not only costly, but can also be psychologically disadvantageous, because after determining the optimal refraction, at least one eye of the test subject has a poor correction, and the test subject must use this poor correction to solve visual tasks in order to determine sensitivity. In the conventional practice, this sequence is necessary because the defined blur for visual acuity measurement can only be adjusted when the optimal refraction is known.

[0225] Accordingly, in one aspect, the object of the present invention is to determine the sensitivity of at least one eye of a test subject in an improved manner and method, in particular simply and quickly, which is required in particular for calculating, optimizing, evaluating and / or manufacturing highly customized and high-quality spectacle lenses. Furthermore, the object of the present invention may be to provide a method and device for calculating, optimizing, evaluating and manufacturing spectacle lenses, which are highly customized and of high quality due to taking into account the sensitivity of at least one eye of the test subject. The object of the present invention may also be to provide such an improved spectacle lens.

[0226] Determining sensitivity as a visual acuity characteristic in the case of a change in the applied optical effect

[0227] In some embodiments, the sensitivity of at least one eye of the test subject is determined as a visual acuity characteristic based on at least two provided visual acuity - refraction value pairs.

[0228] While according to the first alternative, the applied optical effect remains constant and changes, in the second alternative, the size of the pointing characteristic of the adapted visual target remains constant and the applied optical effect changes. The second alternative is subsequently explained in detail.

[0229] In this second alternative, visual acuity - refraction value pairs can be provided by the following steps:

[0230] - Projecting a target (which may comprise at least one adapted visual target) with an adjustable target refraction corresponding to the applied optical effect into at least one eye of the test subject, wherein the target is designed to verify a preset visual acuity; and

[0231] - Determining the visual acuity limit refraction associated with the preset visual acuity of at least one eye of the test subject by changing the target refraction of the target projected into at least one eye of the test subject and detecting the test subject's action, and it is determined by the test subject's action that the identifiability of the target for the test subject has changed at the time point of the test subject's action.

[0232] As described above, the "sensitivity" (with respect to blurring) of at least one eye of a test subject is understood as the correlation of the visual acuity of at least one eye of the test subject with an ametropia, where "ametropia" is the deviation of the effect or refraction provided for at least one eye of the test subject in the determination of visual acuity from the ideal or optimal refraction (target refraction) determined or known for at least one eye.

[0233] "Visual acuity" is a measure of the (central) visual acuity of at least one eye of a test subject. Usually, visual acuity is determined in bright light. In particular, visual acuity can be defined as the reciprocal value of the smallest recognizable gap in a standard test chart, i.e., a Landolt ring. In humans, visual acuity can be determined by an eye test. For this purpose, test charts ("optotypes") are presented to the test subject, and it can be seen from the answers of the test subject whether they are recognized correctly. Visual acuity depends on which test charts the test subject can recognize in the accommodation and / or applied refraction. The test charts usually have a defined size, brightness, shape, and defined contrast. The test charts can be shown on a chart or projected.

[0234] In the method according to the invention, the target for each visual task comprises at least one adapted test chart, where the pointing features are arranged parallel to the selected preferred direction.

[0235] The advantage of using a projector instead of a chart is that it is independent of the test distance. For a reproducible visual acuity test, there are DIN regulations. Accordingly, the standard test chart is the so-called Landolt ring, a ring with a defined width of gaps of the same width, and the gaps can be arranged in eight different directions. By recognizing the direction of the gap, the test subject demonstrates that their resolution ability corresponds at least to the width of the gap. However, in practice, standardized digital images are usually used as test charts because they are easier to understand. There are also other standardized test charts, such as the "Snellen - E", the "Pflüger - E - haken" with a shorter middle line, and other signs suitable for testing the visual acuity of illiterate and preschool children as well as non-verbal communication.

[0236] When determining visual acuity, it is necessary to distinguish between visual acuity with a corrective device (such as glasses or contact lenses) and without a corrective device. Here, the visual acuity without a corrective device is also called the raw visual acuity. The abbreviations "s.c." ("sine correctione", Latin for "without correction") and "c.c." ("cum correctione", Latin for "with correction") are usually also used.

[0237] In particular, the sensitivity of at least one eye can be determined based on a sensitivity metric. By using the sensitivity metric, the sensitivity can be calculated even when the applied refractive values do not have a preset distance from each other.

[0238] The sensitivity metric represents the correlation between visual acuity and (incorrect) refraction. Here, the distance between two refractive values can be part of the sensitivity metric. The sensitivity metric can be defined in the metric space of refractive values. A visual acuity value can be assigned to each refractive value of the sensitivity metric and vice versa. The refractive power can be defined, for example, in at least a three-dimensional space. Thus, the refractive value can generally be described by the coordinates s, c, and α. Here, s can depend on the strength of the spherical optical correction, c depends on the strength of the cylindrical optical correction, and α depends on the axis position of the cylinder. As an alternative to c, the strength of the cylindrical optical correction is sometimes denoted by z. In this metric space of refractive values, the refractive values of a preset first visual acuity and a preset second visual acuity can at least be determined and are thus known when calculating the sensitivity. The sensitivity metric can be used to determine the sensitivity based on two different, essentially arbitrary refractive values. By using such a sensitivity metric, the determination of the sensitivity is independent of the visual acuity measurement at preset refractive values, which is common in conventional methods. Here, on the one hand, the determination of the sensitivity can be independent of the visual acuity measurement at at least one predetermined and / or fixedly preset refractive distance from the refractive result (or from the optimal refraction or target refraction), and on the other hand, it can also be independent of the visual acuity measurement at at least one predetermined and / or fixedly preset relative refractive distance between two applied refractions. Therefore, it is easier for the optometrist and the test subject to obtain the measurement data required to determine the sensitivity.

[0239] Embodiments of the sensitivity metric

[0240] The sensitivity can be calculated with the aid of a metric space in which different refractive values represent individual points. The refractive value can be represented three-dimensionally, for example, using the coordinates s, c, and α. Here, s may depend on the strength of the spherical correction and can be specified, for example, in diopters (which can also be abbreviated as dpt). c may depend on the strength of the cylindrical correction and can be specified, for example, in dpt. α may depend on the axis position of the cylindrical correction and can be specified, for example, in degrees (e.g., from 0° to 180°). Alternatively, other coordinates can be used.

[0241] In the following, it is exemplarily assumed that the optimal refraction (also referred to as the best or ideal refraction within the scope of this specification), i.e., in particular a specific objective and subjective refraction result, is represented by s0, c0, and α0 in this sensitivity measure, and the associated visual acuity is represented by v0. When performing this method, at least two visual acuity - refraction value pairs are provided. Generally, n refractions s i , c i , α i and the associated visual acuity v i can be provided, where i ∈ [1,..., n] and n ≥ 2. Here, at least one visual acuity - refraction value pair of at least one eye of the test subject may already be known and can be provided as a known value pair. This provision includes in particular determination and / or measurement.

[0242] In a possible sensitivity measure, the distance of the refraction i from the optimal refraction in the mean sphere d i and the cylinder α i is calculated using equation (1):

[0243]

[0244] Simple bilinear model of the sensitivity measure with knowledge of the target refraction

[0245] In an embodiment of the bilinear model of the sensitivity measure, for the correlation of visual acuity, the following relationship listed in equation (2) applies to each individual measurement of the refraction i. Here, in a simplified case, it can be assumed that the test subject cannot compensate for the blur by accommodation.

[0246] lgv i = m d ·|d i | + m a ·a i + lgv0 (2)

[0247] Here, m d represents the sensitivity in the spherical distance, and m a represents the sensitivity in the cylindrical distance. This separation between spherical and cylindrical ametropia can be used to take into account that the test subject's response to these two components of ametropia may be very different. Thus, it can be determined from the data of D. Methling: Bestimmung von Sehhilfen [Determination of Visual Aids], 2nd edition, Ferdinand Enke Verlag, Stuttgart, 1996 that, for example, equation (3) applies to the empirically determined average population:

[0248]

[0249] Typically, the above equation (2) has independent parameters m a and m d and v0. Therefore, the system of equations (2) can be clearly solved using three measurements i = 1, 2, 3 of refraction (s1, c1, α1; s2, c2, α2; s3, c3, α3) at three (especially preset) different visual acuity values v1, v2, v3 to give the system of equations (2a):

[0250]

[0251] where denominator = (a2 - a3)|d1|+(a3 - α1)|d2|+(a1 - a2)|d3| (2a)

[0252] Here, the visual acuity measurement can be carried out, for example, under optimal correction conditions, that is, in the target refraction (especially obtained from objective and / or subjective refraction measurements). Subsequently, for example, when i = 3, it applies that: (s3, c3, α3) = (s0, c0, α0). In this optimal correction condition, α3 = α0 = 0 and d3 = d0 = 0. Therefore, the third in equation (2a) is automatically satisfied. Subsequently, the other equations take the following form of the system of equations (4):

[0253]

[0254] where denominator = a2|d1|-a1|d2| (4)

[0255] Therefore, the system of equations (4) provides an example of a simplified bilinear model of the sensitivity metric. The system of equations (4) can be solved with the knowledge of the target refraction and the knowledge of two additional refraction values for two additional visual acuity values (for i = 1, 2). The visual acuity - refraction value pairs used here can be obtained using the method according to the invention. Therefore, the sensitivity can be obtained from the system of equations (4). The sensitivity describes the correlation between visual acuity and (error) refraction. This can be described, for example, by the values m a and m d

[0256] If, in addition to the visual acuity v0 in the target refraction, more than two additional refractions are measured among the preset visual acuity values, then m d and m a can be more precisely obtained for the sensitivity by a compensation method (such as the least squares method) from all the data. In addition, outliers can be excluded from the measurement data to improve the quality of sensitivity determination.

[0257] Simplified linear model of the sensitivity metric with knowledge of the target refraction​

[0258] In a more simplified and less customized model of the sensitivity metric, for example when only one measurement is available at an incorrect refraction i = 1, the relationship between the spherical refraction distance and the cylindrical refraction distance can be assumed according to Equation (5):

[0259] m d = m

[0260] m a = f·m d = f·m (5)

[0261] Here, the parameter f can be derived from empirical values and can be, for example, a scalar. Using the assumption according to Equation (5), the system of equations (2) simplifies to give the following Equation (6):

[0262] lgv i = m·(d i + f·a i ) + lgv0lgv i = m·(a i + f·d i ) + lgv0 (6)

[0263] Therefore, the sensitivity m can be obtained from the measurement at the incorrect refraction i according to Equation (7):

[0264]

[0265] The value of f can be derived from relevant literature. For example, f = 1 / 2 can be set, which is derived from Applegate, R.A, Sarver, E.J, Khemsara: "Are all aberrations equal?", J Refract Surg. 2002, 18: pp. 556 - 562. Or f = 1 can be set, which is derived from Atchison et al.: "Blur limits for defocus, astigmatism, and trefoil", Vision Research, 2009.

[0266] Here, a linear relationship does not necessarily have to be assumed for Equation (5). Alternatively, a more complex relationship can be formed, and for example, the sensitivity can be derived therefrom according to multiple independent parameters and / or refraction measurements by introducing the corresponding analytical relationships, see Equations (4) and (7). The sensitivity can also be derived from compensation methods, such as the least squares method.

[0267] Additional models of the sensitivity metric with knowledge of subjective refraction

[0268] The sensitivity can also be calculated based on another model. For example, the following models are known from R. Blendowske, "Unassisted Visual Acuity and Blur: The 'Simple Model'", Optometry and Vision Science, Vol. 92, No. 6, 2015. These models are characterized by particularly simple properties and are based on only a few parameters. These simple models are particularly suitable for calculating sensitivity and adaptation in low-data situations, for example because they can effectively avoid overfitting.

[0269] If a larger number of parameters are available individually, then a model with multiple different parameters is more suitable, such as as described in the document DE 10 2017 007 663 A1.

[0270] In principle, multiple different models can be used. Here, the model used in individual cases may depend on the number of visual acuity - refractive value pairs provided or determined. In a sufficient number of visual acuity - refractive value pairs, a relatively complex, not necessarily linear model can be formed, and its parameters can be adapted to the measurements.

[0271] The models listed above by way of example can be generalized, such as by describing a function of visual acuity that includes the contour of constant visual acuity in the power vector space, and the contour corresponds to an ellipsoid or ovoid containing the point with the maximum visual acuity. This can be carried out in a manner similar to the method proposed in A. Rubin and W. F. Harris: "Closed Surfaces of Constant Visual Acuity in Symmetric Refractive Space", Optometry and Vision Science, Vol. 78, No. 10, 2001. Here, the axial ratio can vary in the range of 0.25 to 4 respectively. Instead of the individually measured values, the mean, median or other estimated values of the corresponding model parameters of the population can also be used to calculate the visual acuity.

[0272] In an embodiment, the generalization of the above equation (6) results in different factors f, such as equation (8):

[0273]

[0274] Here, and represent the astigmatism of refractive error with orthogonal (J0) and tilted (J45) axis positions, and are defined as:

[0275]

[0276] Here, R represents the rotation matrix, which determines in the vector Orientation of the ellipsoid of constant visual acuity in the power vector space. The eigenvalues m1, m2, m3 represent the sensitivities to defocus in the directions of the first column vector, the second column vector, and the third column vector of the rotation matrix R in the power vector space.

[0277] Implementation of a model of a sensitivity measure without knowledge of the target refraction

[0278] In some embodiments, the sensitivity can be determined without knowing or determining the target refraction. This can occur when determining the relevant refraction or the refractive limit of visual acuity for multiple preset different values of visual acuity, respectively. In this case, the optimal refraction or the target refraction can be determined from the measurement data collected here. In addition, the actually determined optimal refraction can be checked using the model of the sensitivity measure from the measurement data.

[0279] Here it can be assumed that the test subject can compensate for defocus in the negative direction, i.e., deliberate incorrect refraction, by accommodating at least one eye. In this case, the point at which the visual acuity curve bends can be selected in the linear model according to the above equations (2) and (6). In a non-linear model with saturation, the optimal refraction can be directly calculated as a parameter of the system of equations. For this purpose, in the corresponding formula, i.e., especially already in equation (1), the incorrect refraction, i.e., the distance d i and a i must be replaced by the difference between the optimal refraction and the adjustment or applied correction.

[0280] The above-described implementation of the model of the sensitivity measure is an example of how the sensitivity can be determined within the scope of the present invention.

[0281] The target can in particular be a real target (or real object) or a virtual target (or virtual object). In particular, the target can be a real object or a virtual projected object (or a projected virtual object). The target can be realized, for example, by a display (e.g., having one or more lenses and / or one or more mirrors), by a light field display, and / or by a Badal optometer (which enables a constant magnification despite changing effects), and can be projected into at least one eye of the test subject.

[0282] A "virtual object" or "virtual target" is in particular understood as an optical imaging system that generates wavefronts emitted from virtual object points such that they irradiate at least one eye of the test subject. Here, the wavefronts generated by the virtual target (corresponding to the virtual object points respectively) and irradiating at least one eye of the test subject can have an adjustable spherical curvature and / or an adjustable cylindrical curvature component, where the cylindrical curvature component is preferably adjustable both with respect to the curvature value and with respect to the axis position.

[0283] The virtual position of the virtual object (target) can preferably be changed such that in this way different accommodation states of at least one eye can be stimulated. In particular, the position of the virtual object can preferably be changed between a position for stimulating hyperopic accommodation and a position for stimulating myopic accommodation. Additionally, the position of the virtual object can preferably be adjusted such that at least one eye of the test subject can no longer accommodate the virtual object. In this case, the virtual object (target) can only be perceived by the test subject as blurred in all directions. This results in the ciliary muscle relaxing. This state is referred to as the "blur" state.

[0284] A target with an adjustable or variable target refraction (or target effect) is projected into at least one eye of the test subject. This projection can be carried out by means of an optical system with which the effect or refraction of the target, i.e., the target refraction, can also be adjusted and / or changed. Thus, within the scope of the present invention, "target refraction" is understood as the refraction (especially spherical and / or astigmatic refraction) with which the target is projected into at least one eye of the test subject or the target is provided to at least one eye of the test subject (applied or caused by the optical system).

[0285] In particular, the optical projection that enters or is projected onto the eye of the test subject is considered as the target such that this projection generates an image on the retina of the eye that corresponds to the image of a real object at a certain distance from the eye. This specific distance is also referred to herein as the virtual position of the virtual target. In other words, in the sense of this specification, the target is in particular the imaging of an object into at least one eye of the test subject. For example, a backlit transparency can be used as the object. Since in the case of the virtual target the target is not (directly) the real object at the virtual position, the virtual position can also be infinitely simulated by appropriately constructing the optical system for the projection. This corresponds to a wavefront that converges towards the eye (i.e., in the propagation direction).

[0286] Projecting a target (especially a virtual target) into at least one eye of the test subject by means of an optical system is in principle known and will therefore not be discussed in more detail within the scope of the present invention. For example, the projection of a target into at least one eye of the test subject is described in K. Nicke and S. Trumm: " der Zukunft - Schritt 3Der DNEye Scanner", Optician, June 2012 or also in the document DE 10 2013 000 295 A1.

[0287] The target projected into at least one eye of the test subject is designed to verify a preset, in particular predefined and / or known visual acuity (or a preset visual acuity level). Herein, "verifying the preset visual acuity" should be particularly understood as meaning that by means of the target, it can be determined or ascertained (in particular based on the actions of the test subject) whether at least one eye of the test subject has reached the preset visual acuity or the preset visual acuity level. In other words, the target presets a specific visual acuity or a specific visual acuity level, and it can be determined whether at least one eye of the test subject has reached it (in particular based on the actions of the test subject). In particular, the target (in particular its size) is provided such that a preset visual acuity or a preset visual acuity level can be assigned or is assignable to the virtual target. In other words, the target is a target with a preset visual acuity or a preset visual acuity level. This means that if at least one eye of the test subject at least reaches or has the visual acuity preset by the target or the visual acuity level preset by the target, then the test subject can recognize or be able to identify the target, in particular in the case of ideal refraction or in the correction of a possible visual defect of at least one eye of the test subject. The visual acuity level is associated with and / or depends on the size of the pointing feature of the adapted optotype.

[0288] In particular, the target can comprise or be suitable for determining visual acuity with an adapted optotype. Herein, the size or dimension of the pointing feature of the optotype depends on the preset visual acuity or the preset visual acuity level. In particular, the size or dimension of the pointing feature of the optotype is selected such that only a test subject with a visual acuity of at least corresponding to the preset visual acuity or the preset visual acuity level can recognize and / or identify the pointing feature of the optotype.

[0289] The target can also be an image or photograph containing two or more details, the recognition of which can be respectively assigned to a preset visual acuity or a preset visual acuity level. The image can in particular show an object (such as a road extending into the distance, the sky, a balloon in the distance, etc.), which can create a sense of openness or distance in the observer. The above-mentioned details contained in the image (such as a symbol or panel on a hot air balloon or a hot air balloon basket, a symbol in a cloud or a cloud, a line on a road, a symbol on a roadside sign, etc.) are explicitly included in the context of this specification by the term "optotype". Particularly suitable symbols as optotypes are for example one or more concentric rings, which merge into a circle at a given blur.

[0290] The visual acuity or the visual acuity level of a target, multiple targets or optotypes can be determined in a known manner, for example, by calculating the viewing angle of the details or by identifying a test subject with known visual acuity characteristics.

[0291] After projecting a target into at least one eye of a test subject, the visual acuity limiting refraction associated with a preset visual acuity or a preset visual acuity level of at least one eye of the test subject is determined.

[0292] The "visual acuity limiting refraction" or "visual acuity level limiting refraction" is understood to be the following refraction or limiting refraction in or from which the identifiability of the target of the test subject changes. In particular, the "visual acuity limiting refraction" or "visual acuity level limiting refraction" is understood to be the following refraction or limiting refraction, in which the test subject

[0293] a) can start from a blurred state and identify and / or identify a target provided for it or a virtual target projected into at least one of its eyes by changing the target refraction (applied or caused by the optical system), the target or virtual target being characterized by a preset visual acuity or a preset visual acuity level, or

[0294] b) can start from a non-blurred state and just no longer be able to identify and / or identify a target provided for it or a virtual target projected into at least one of its eyes by changing the target refraction (applied or caused by the optical system), the target or virtual target being characterized by a preset visual acuity or a preset visual acuity level.

[0295] The visual acuity limiting refraction is determined by changing the target refraction of the target projected into at least one eye of the test subject and by detecting the test subject's action (such as the test subject's message or input, in particular the operation of a button or a joystick). The target refraction can be changed gradually or preferably continuously. Preferably, the target refraction changes monotonically and / or constantly. Signaled or determined by the test subject's action is that, at the time point of the test subject's action, the identifiability of the target for the test subject has changed. In other words, the test subject signals by means of the test subject's action that the target is first recognized or identified in the target refraction present or applied at the time point of the test subject's action, or that the target can no longer be recognized or identified for the first time or just no longer. In particular, the visual acuity limiting refraction corresponds to the target refraction or target effect present or applied by the optical system at the time point of the test subject's action.

[0296] Therefore, taking into account the preset visual acuity or the preset visual acuity level and the determined associated visual acuity limiting refraction, the sensitivity of at least one eye of the test subject is determined. For this purpose, an adapted visual target can be used, the size of whose pointing feature is assigned to a preset visual acuity value or a preset visual acuity level.

[0297] This method can in particular be carried out within the scope of autorefraction or aberration measurement. For this purpose, at least one pair of visual acuity levels and associated application effects are detected. This is achieved by means of the signals of the test subject during a change in the application effect in a target with a defined visual acuity level (i.e., a defined optotype size).

[0298] As previously mentioned, in order to determine the sensitivity, at least two pairs of visual acuity levels and associated application effects are required. In the conventional method, within the defined application effects, it is determined at which visual acuity level the test subject respectively reaches with these effects (i.e., from which size the test subject can still recognize the optotype). In contrast, in a variant of this method, the size of the pointing feature of the adapted optotype (and thus the visual acuity level) remains constant for at least one of these pairs, and the application effect changes. The test subject emits a signal when the test subject can still recognize or can no longer recognize the adapted optotype with a defined size.

[0299] Differently from the prior art, in this alternative, in order to determine the sensitivity, the visual acuity level of a specific application effect (with a priori known or a priori unknown refractive error) is not required, but rather the application effect required to achieve a preset visual acuity is required.

[0300] This method allows the sensitivity to be determined in a simple and rapid manner. In particular, this method allows the sensitivity (as a subjective measurement parameter) to be determined in a simple manner during normal objective refractive measurement without great additional effort. In particular, during subjective refraction, complex measurements can be avoided, and psychologically unfavorable steps can be omitted, where, after determining the optimal refraction, the test subject is provided with a poorer correction and thus should solve a visual task. In addition, this method can advantageously be very well associated with other measurements for determining individual parameters of advanced spectacle lenses (such as myopia measurement, pupil measurement, corneal pigmentation) and measurements in optometry or ophthalmic screening or measurements for establishing findings (such as corneal pigmentation, opacity, thickness measurement, tomography, intraocular pressure measurement or retinal imaging).

[0301] In an embodiment, before the step of projecting a target designed to verify (or determine) a preset visual acuity into at least one eye of a test subject, an objective and / or subjective refractive result of at least one eye of the test subject is determined (in particular a refractive result based on a combination of objective and subjective measurements, where additional data, such as low-order and / or high-order aberrations from an aberrometer or other biometric data, such as corneal shape, distance between the lens and the retina, anterior chamber depth, etc.). The "refractive result" is particularly understood as the determined refractive value. In this way, compared with previous methods, the determination of sensitivity can be associated with one or more aberration measurements or autorefraction measurements. In particular, the determination of visual acuity can be associated with the measurement of autorefraction or aberration data in a non-accommodated state and an accommodated state.

[0302] Preferably, the objective refractive value or objective refractive result is determined in a blurred state. For this purpose, a target (such as an image or a photograph) can be presented to the test subject, or a corresponding virtual target can be projected into at least one eye of the test subject (by means of an optical system), which has the effect of causing the test subject to only recognize the target as blurred (or not completely clear), thereby achieving relaxation of the ciliary muscle of at least one eye of the test subject. Compared with the best refraction of at least one eye of the test subject, this degree of blurring can be, for example, with an additional effect of approximately 1.25 dpt to 1.5 dpt.

[0303] In a special embodiment, the accommodation state of the eye can also be tracked in order to thus obtain a more reliable sensitivity value.

[0304] Preferably, before the step of changing the target refraction, the target is projected into at least one eye of the test subject at the starting target refraction, i.e., the optical effect applied first, at least in the selected preferred direction, such that the test subject can only recognize a blurred (or not completely clear) target and / or cannot identify it. In other words, the starting target refraction is preferably selected such that the test subject cannot focus the target or the adapted visual target by accommodation. This is achieved in particular in such a way that the starting target refraction is shifted in the positive direction compared to the best refraction of at least one eye of the test subject. Only by changing the target refraction in the negative direction can the state be reached in which the test subject can recognize and / or identify the target or the visual target. This has the additional advantage that the test subject initially does not know the target or the visual target and thus performs the test subject action at the correct point in time with a higher probability, i.e., only when it can actually identify the target or the visual target. However, if the test subject already knows the target or the visual target beforehand or at the start of the measurement (due to the corresponding starting target refraction at which it sees the target or the visual target sharply), it is recognized within the scope of the present invention that this approach, although alternatively possible, may not be as accurate and reliable as the above-described preferred embodiment. This is because a test subject who already knows the target or the visual target beforehand tends to signal the point in time slightly too late at which or from which the test subject can no longer recognize and / or can no longer identify the target or the visual target just after the change of the target refraction in the positive direction.

[0305] In a further embodiment, before or after the step of projecting a target designed to verify a preset visual acuity into at least one eye of a test subject and determining a visual acuity limit refraction associated with the preset visual acuity of the target, the method includes determining the best refraction (target refraction) of at least one eye of the test subject. In particular, the method may include determining an objective and / or subjective refraction or an objective and / or subjective refraction result. Determining the best refraction may also include determining a combined refraction or a combined refraction result based on objective and / or subjective refraction measurements, where in particular, additional data of at least one eye of the test subject, such as low-order and / or high-order aberrations from an aberrometer, or additional biometric data, such as corneal shape, lens-to-retina distance, anterior chamber depth, etc., are also considered. In this sense, the terms "refraction" and "target refraction" (or "refraction result") should be combined with "best refraction" and are not limited to the correction of low-order aberrations (e.g., spherical and astigmatic), but they may also include higher-order aberrations. Thus, the term "refraction" can generally also be understood as "correction". Preferably, the best refraction of at least one eye of the test subject is determined in a blurred state, which can be achieved by providing a corresponding target or projecting a corresponding target into at least one eye of the test subject (see above). In addition, according to this preferred embodiment, the visual acuity achieved by at least one eye of the test subject when compensating for any visual defects of at least one eye of the test subject (e.g., based on the determined best refraction) is determined. In other words, after the visual defect determined by refractive measurement has been substantially corrected by an optical system or by a lens (the effect of which corresponds to the determined refraction result), the visual acuity, i.e., visual acuity cum correctione (VCC), is determined. The visual acuity can be determined using known methods. In particular, the determined best refraction and the measured relevant visual acuity represent one of at least two visual acuity-refraction value pairs provided, which are used or considered when determining the sensitivity. In this way, the determination of the sensitivity can be combined with or integrated into the measurement of objective and / or subjective refraction. Therefore, the sensitivity can be determined quickly and simply, especially in combination with other measurements.

[0306] In a further embodiment, preferably after projecting a target designed to verify a preset visual acuity into at least one eye of a test subject and after determining a visual acuity limit refraction associated with the preset visual acuity of the target, the method further includes the following steps:

[0307] - determining a subjective refraction result or a subjective refraction of at least one eye of the test subject;

[0308] - Determine the visual acuity achieved by at least one eye of the test subject based on the determined subjective refractive result when compensating for any visual defects of at least one eye of the test subject.

[0309] The determined subjective refraction and the visual acuity determined in this determined subjective refraction of at least one eye of the test subject preferably represent a pair (or another pair, especially the second pair, the third pair, the fourth pair, etc.) in the visual acuity - refractive value pairs provided by the method for determining sensitivity.

[0310] Furthermore, the method preferably includes determining the optimal refraction of at least one eye of the test subject based on the subjective refractive result and the objective refractive result. The optimal refraction is especially the combined refraction of the subjective and objective refractive results. It is in principle known to obtain the combined refractive result from the objective and subjective refractive measurements, and thus it is not explained in detail within the scope of this specification. The combined refraction can be obtained, for example, in such a way that the objective refractive measurement is first performed and the objective refractive result is adapted by means of the subsequently performed subjective refraction. It is especially also possible to obtain the combined refraction by forming the average of the objective and subjective refractions.

[0311] In a further embodiment, the sensitivity is determined by means of at least one calculated incorrect refraction, wherein at least one calculated incorrect refraction is calculated based on the determined optimal refraction. Here, the optimal refraction can be the determined objective and / or subjective refraction. In particular, the optimal refraction can be the combined refraction of the objective refraction and the subjective refraction.

[0312] Preferably, the incorrect refraction is determined "after the fact", that is, only after a target designed to verify a preset visual acuity is projected into at least one eye of the test subject and after determining the visual acuity limiting refraction related to the preset visual acuity of the target. Preferably, the incorrect refraction is determined only after determining at least one visual acuity - refractive value pair. Preferably, the incorrect refraction is determined after performing the objective and / or subjective refractive measurements and especially after obtaining the ideal refraction or the ideal refractive result from the objective and subjective refractive measurements. In a preferred embodiment, the following steps can be performed, for example, especially in the stated order:

[0313] 1) Perform an objective refractive measurement (within the scope of the method according to the invention);

[0314] 2) Determine at least one visual acuity - refractive value pair (within the scope of the method according to the invention);

[0315] 3) Perform a subjective refractive measurement;

[0316] 4) Obtain the ideal refraction or the ideal refractive result based on the objective and subjective refractive measurements; and

[0317] 5) Starting from the result of step 4, i.e., calculating the refractive error and sensitivity based on the desired refractive power or the result of the desired refractive power obtained.

[0318] In a further embodiment, changing the target refractive power includes monotonically decreasing the target refractive power and / or monotonically increasing the target refractive power

[0319] In a further embodiment, the visual acuity limit refractive power associated with a preset visual acuity of at least one eye of the test subject is determined by decreasing the target refractive power and detecting the test subject's movement during the decrease of the target refractive power, and / or by increasing the target refractive power and detecting the test subject's movement during the increase of the target refractive power, wherein it is determined with each test subject movement that the identifiability of the test subject's target has changed at the time point of the corresponding test subject movement. In this way, the "out-of-focus point" is approached from different directions. In other words, the out-of-focus point can be determined when increasing the target refractive power, and another out-of-focus point can be determined when decreasing the target refractive power. These out-of-focus points may be different from each other and are then averaged. In particular, within the range of minimizing the squared error, the sensitivity can be determined from the two out-of-focus points with the aid of known metrics.

[0320] In a further embodiment, at least two of the provided visual acuity - refractive power value pairs are provided by the following steps:

[0321] - Projecting a first target with an adjustable and / or variable first target refractive power into at least one eye of the test subject, wherein the first target is designed to verify a preset (predetermined and / or known) first visual acuity (or preset first visual acuity level);

[0322] - Determining the first visual acuity limit refractive power associated with the preset first visual acuity (or preset first visual acuity level) of at least one eye of the test subject by changing (in particular continuously, monotonically and / or constantly changing) the first target refractive power of the first target projected into at least one eye of the test subject and detecting the first test subject movement, and using the first test subject movement to signal or determine that the identifiability of the first target of the test subject has changed at the time point of the first test subject action;

[0323] - Projecting a second target with an adjustable and / or variable second target refractive power into at least one eye of the test subject, wherein the second target is designed to verify a preset (predetermined and / or known) second visual acuity (or preset second visual acuity level), which is different from the preset first visual acuity (or preset first visual acuity level);

[0324] - By changing (especially continuously, monotonically, and / or constantly) the second target refractive power projected into at least one eye of the test subject and detecting the second test subject movement, the second visual acuity limit refractive power associated with a preset second visual acuity (or a preset second visual acuity level) of at least one eye of the test subject is obtained. Signaled or determined by using this second test subject movement is that the identifiability of the second target of the test subject is changed at the time point of the second test subject movement.

[0325] In particular, the sensitivity of at least one eye of the test subject is determined in the case of using or considering the preset first visual acuity and the obtained associated first visual acuity limit refractive power, and in the further case of using or considering the preset second visual acuity and the obtained associated second visual acuity limit refractive power. Preferably, the preset first visual acuity or the preset first visual acuity level of the first target is less than the preset second visual acuity or the preset second visual acuity level of the second target. For example, the preset first visual acuity or the preset first visual acuity level may have a value of 0.8 logMar, while the preset second visual acuity or the preset second visual acuity level has a value of 1.0 logMar. Or for example, the preset first visual acuity or the preset first visual acuity level may have a value of 0.4 logMar, while the preset second visual acuity or the preset second visual acuity level has a value of 0.8 logMar or 1.0 logMar. It is understood that other values can also be selected. Preferably, the change in the preset visual acuity or the preset visual acuity level from one virtual target to the next is in the range of 0.2 logMar to 0.7 logMar, preferably in the range of 0.2 logMar to 0.5 logMar, and particularly preferably in the range of 0.2 logMar to 0.3 logMar.

[0326] In another embodiment, determining the refractive limit of visual acuity includes measuring and / or monitoring the accommodation state of at least one eye of a test subject, wherein the measurement of the accommodation state is performed especially at or immediately after the time point of the movement of the test subject. The result of such measurement or monitoring can be used to control the progress (for example, in the case of an undesired accommodation (for example, exceeding a certain threshold), terminating or repeating individual steps). The measurement can be performed not only continuously but also only during or immediately after the movement of the test subject. Additionally, the accommodation state (spherical, cylindrical, low-order or high-order aberration) measured ideally at the time point of the movement of the test subject can be included in the calculation of sensitivity or refractive error. For example, the accommodation value can be the distance value obtained by subtracting the application effect from the refractive value of hyperopia. Expressed by a formula, the following formula applies to the simplest case: The sensitivity expresses the visual acuity V as a function f of the refractive error F, i.e., V = f(F). Here, the refractive error F is

[0327] - in the case of no accommodation, the difference between the actual application effect T and the ideal effect I, i.e., F = T - I; and

[0328] - in the case of accommodation, the difference between the actual application effect T and the currently measured effect G a therebetween, i.e., F = T - G a .

[0329] When there is a deviation D between the ideal effect I and the measured effect (effect G0) when the eye is relaxed, the following formula applies: I = G0 + D. Therefore, in this case, F = T - (G0 + D) or F = T - (G a + D). For the spherical value, the formula can be used in the described manner. For the cylindrical value, the crossed-cylinder formula should be used accordingly. Zernike coefficients (also for high-order aberrations) or power vectors can be used similarly.

[0330] Alternatively or additionally, determining the visual acuity limiting refraction may include measuring and / or monitoring the pupil size (e.g., pupil radius) of at least one eye of the test subject, wherein the pupil size is measured especially at or immediately after the time point of the test subject's movement. The pupil size can be measured, for example, by a camera (which is part of the refraction unit, i.e., an auto-refractor or an aberrometer, for example) or by a separate camera. The pupil size measured at the time point of the test subject's movement (i.e., at the defocus point) or correspondingly before or after (e.g., up to 2 seconds before reaching the defocus point) can be used to determine the sensitivity of at least one eye of the test subject with respect to blur. In particular, the measured pupil size can be used to quantify the blur of the image on the retina, preferably with the aid of a suitably parameterized eye model and a known additional blur. A simpler description can also be used instead of the complete eye model. For example, the following angle can be calculated: at this angle, the circle of confusion of a point shown blurred can be observed in a given pupil and a given additional blur (for this see, for example, WO2019 034525A1). The sensitivity can be determined within the scope of such a visual acuity model as the deterioration of the visual sharpness per angle of the circle of confusion.

[0331] In a further embodiment, to determine the visual acuity limiting refraction, a visual task with at least two, preferably at least three, particularly preferably at least four, especially four or eight possible different answers is presented to the test subject, wherein the test subject can respond to the visual task by means of the test subject's movement. A "visual task" is understood here in particular as a task with a predefined and thus verifiable solution. In particular, the visual task is thus a verifiable task (i.e., its solution is known and thus a verifiable visual task). In other words, the test subject's movement not only conveys the recognizability or identifiability of the target. Preferably, the visual task is based on forced choice, i.e., the test subject is "forced" to make a choice from multiple or at least two or more possible answers, where the correct answer is preferably predefined or known. Here, such a visual task is called a "forced choice" visual task. Solving the visual task or making a choice can be done, for example, by means of a joystick, which the test subject can use to activate different directions. For example, the visual task can be that the test subject has to identify the position or direction of a notch in an adapted optotype by means of a joystick. If the adapted optotype is, for example, a Landolt ring, then there are two possible positions for this, and thus two possible answers for the test subject, for example, the pointing feature can be arranged parallel to the selected preferred direction. It is to be understood that other optotypes can also be used in principle, such that the test subject has answers related to the adapted optotype. In this way, the method becomes more accurate and reliable compared to when the test subject only has to give unverified feedback (e.g., "yes" or "no" or "recognizable" or "not recognizable").

[0332] In a further embodiment, before the step of determining the limiting refractive power for visual acuity, it is preferred to detect first aberration data of at least one eye of the test subject for the far accommodation state and / or the defocus state of at least one eye of the test subject and in particular in a first luminance. In addition, the method preferably includes detecting second aberration data of at least one eye of the test subject for the near accommodation state of at least one eye of the test subject, in particular in a second luminance whose value is lower than the first luminance. Here, it is preferred to detect the second aberration data before the step of determining the limiting refractive power for visual acuity. In the context of the present description, "aberration data" (or "aberration measurement") is understood to mean data for describing eye aberrations (measurements for obtaining this data), which, when represented by Zernike coefficients, has an information content corresponding at least to the term of the "defocus" order, but ideally includes higher orders (such as coma and spherical aberration). In particular, "aberration data" may also include or be (pure) autorefraction data. In particular, detecting aberration data also includes detecting (pure) autorefraction data (i.e., sphere and / or cylinder and / or axis). The luminance in the mesopic vision mode is preferably provided as the first and second luminance respectively (preferred optical densities are in the range of about 0.003 cd / m 2 to about 30 cd / m 2 range, particularly preferably in the range of about 0.003 d / m 2 to about 3 cd / m 2 range, more preferably in the range of about 0.003 cd / m 2 to about 0.3 cd / m 2 range, most preferably in the range of about 0.003 cd / m 2 to about 0.03 cd / m 2 range). Herein, in particular, the luminance is always understood as the luminance at the eye position or the luminance detected by the eye.

[0333] Together with the detection of the first aberration data and / or the detection of the second aberration data (i.e., in particular in the first or second luminance and in the first accommodation state or the second accommodation state), it is also possible to detect first pupillometry data and / or second pupillometry data of at least one eye of the test subject. Here, the term "pupillometry data" (or pupillometry value) refers to information about the pupil size (or the measurements for obtaining these data), which includes at least one size specification (e.g., in the form of a radius), but can also reproduce the shape of the pupil in a more complex form. In addition, the pupillometry data may contain information about the pupil position (e.g., relative to the corneal apex or the optical axis of the eye).

[0334] On the other hand, it relates to a method for calculating, optimizing or evaluating spectacle lenses for at least one eye of a test subject or a spectacle wearer, taking into account the sensitivity of at least one eye of the test subject, wherein the sensitivity of at least one eye of the test subject is determined by one of the methods according to the invention.

[0335] In particular, the method for calculating, optimizing or evaluating spectacle lenses for at least one eye of a test subject may comprise the following steps:

[0336] a) Providing an assignment of at least one imaging property or aberration of the spectacle lens system to the visual acuity of the spectacle wearer or a typical spectacle wearer when observing an object through the spectacle lens system;

[0337] b) Determining or presetting an objective function for the spectacle lens to be calculated or evaluated, in which the assignment from step (a) will be evaluated;

[0338] c) Calculating or evaluating the spectacle lens to be calculated or evaluated by evaluating the objective function, wherein the objective function is evaluated at least once.

[0339] The assignment of at least one imaging property or aberration of the spectacle lens system to the visual acuity of the spectacle wearer may depend parametrically on the measured output visual acuity and / or the measured sensitivity of the spectacle wearer. The calculation and / or optimization of the spectacle lens may in particular comprise minimizing or maximizing the objective function. The method for calculating, optimizing or evaluating spectacle lenses may further comprise calculating at least one light beam emerging from the object in at least one viewing direction by means of wavefront calculation, ray calculation or wave field calculation through the spectacle lens system and / or through the spectacle lens to be calculated or evaluated up to the evaluation surface in the spectacle lens system. Furthermore, the method for calculating, optimizing or evaluating spectacle lenses may comprise calculating the difference present at the evaluation surface between the light beam emerging from the object and a reference light beam converging on the retina of a model eye, and determining at least one imaging property or aberration based on the calculated difference. Preferably, at least one light beam emerging from the object is calculated by means of wavefront calculation, wherein calculating the difference present at the evaluation surface comprises calculating the wavefront difference between the wavefront of the light beam emerging from the object and the wavefront of the reference light beam converging on the retina, and the wavefront difference at the evaluation surface is calculated. In addition, the method for calculating, optimizing or evaluating spectacle lenses may comprise assigning a geometric optical angle and / or a quadratic form in a geometric optical angle space to the calculated wavefront difference, wherein at least one imaging property or aberration depends on at least one component of the geometric optical angle and / or the quadratic form.

[0340] Alternatively or additionally, the method for calculating, optimizing or evaluating spectacle lenses may comprise the following steps:

[0341] - Preset a first surface and a second surface for the spectacle lens to be calculated or optimized;

[0342] - Determine the path of the principal ray passing through at least one viewing point on at least one surface of the spectacle lens to be calculated or optimized and entering the model eye;

[0343] - Evaluate the aberration of the wavefront generated by the spherical wavefront incident on the first surface of the spectacle lens along the principal ray at an evaluation surface, compared with the wavefront converging at a point on the retina of the eye model;

[0344] - Iteratively change at least one surface of the spectacle lens to be calculated or optimized until the evaluated aberration corresponds to a preset target aberration.

[0345] On the other hand, it relates to a method for manufacturing a spectacle lens, including:

[0346] - Calculate or optimize the spectacle lens according to the method for calculating or optimizing the spectacle lens according to the present invention; and

[0347] - Manufacture the thus calculated or optimized spectacle lens.

[0348] Furthermore, the present invention provides a computer program product, especially in the form of a storage medium or a data stream, which contains program code designed to execute the method according to the present invention when loaded and executed on a computer, especially for determining the sensitivity of at least one eye of a test subject and / or for calculating, optimizing or evaluating a spectacle lens and / or for manufacturing a spectacle lens. In other words, the present invention provides a computer program product including machine-readable program code that is suitable for executing the above-mentioned method according to the present invention when the program code is loaded on a computer. In particular, the computer program product should be understood as a program stored on a data carrier. In particular, the program code is stored on a data carrier. In other words, the computer program product includes computer-readable instructions that, when loaded into the memory of a computer and executed by the computer, cause the computer to execute the method according to the present invention.

[0349] In particular, the present invention provides a computer program product containing program code that is set and designed to execute the method according to the present invention for determining the sensitivity of at least one eye of a test subject and / or the method according to the present invention for calculating, optimizing or evaluating a spectacle lens, and / or the method according to the present invention for manufacturing a spectacle lens when loaded and executed on a computer.

[0350] On the other hand, it relates to a device for determining the sensitivity of at least one eye of a test subject, including:

[0351] - A target providing device for providing a target, which is designed to verify a preset visual acuity and configured to show at least one adapted visual acuity chart;

[0352] - An optical system for projecting a target with a target refractive power into at least one eye of a test subject, wherein the optical system is designed to adjust and change the target refractive power;

[0353] - A feedback unit for detecting the actions of the test subject in order to determine that at the time point of the actions of the test subject, especially in changing the target refractive power of the target projected into at least one eye of the test subject by means of the optical system, the identifiability of the target of the test subject has changed; and

[0354] - A visual acuity limit refractive power obtaining unit for obtaining the visual acuity limit refractive power associated with the preset visual acuity of at least one eye of the test subject, wherein the visual acuity limit refractive power is designed to detect (especially determine and store) the target refractive power caused by the optical system at the time point of the actions of the test subject.

[0355] The target providing device can, for example, include an electronic display or a digital screen. In particular, the display can be designed such that individual pixels of the display, different regions of the display or different components can be individually controlled, especially in order to show a combined optometric font. For example, sub-segments of a ring can be shown, with which Landolt-C optometric fonts with openings of different orientations can be generated or shown. Alternatively or additionally, complete optometric fonts, such as letters or numbers, can also be constructed as integral and especially switchable LCD elements. Generally, the display is configured to show adapted visual acuity charts.

[0356] The target providing device can, for example, include a folding mechanism or a displacement mechanism or a rotating mechanism, which is, for example, magnetic or electric, by means of which different targets or images can be shown and / or replaced. The target or image can also be partially transparent and only contain the regions that should be shown in addition to other images.

[0357] The transparent backlit image can also be designed such that only specific parts of the image can be seen when one or more specific light sources (e.g., in a shadow region or with a specific wavelength) are turned on or off.

[0358] The optical system is particularly arranged between at least one eye of the test subject and the target providing device or the provided target. The optical system can be configured as a refractive unit. The optical system is designed to apply or induce different target effects as optical effects, at least in a selected preferred direction, and thus affect the recognizability of the target for at least one eye of the test subject. Here, the optical system can be designed to provide different spherical effects as optical effects. This can be achieved, for example, by arranging one or more spherical lenses, for example in the form of a Badal system. Alternatively or additionally, one or more adaptive lenses can be used or arranged, optionally in combination with conventional lenses. In more complex cases, in addition to or instead of the spherical effect, the optical system can be designed to apply or induce different cylindrical effects or higher-order effects.

[0359] The optical system can have at least one lens with a spherical effect and / or at least one lens with a cylindrical effect. For example, the optical system can include a magazine with a plurality of spherical lenses and / or cylindrical lenses, the spherical lenses and / or cylindrical lenses each having a different spherical effect or cylindrical effect, and wherein the magazine is designed and arranged such that the individual spherical lenses or individual cylindrical lenses of the magazine and / or combinations of a plurality of spherical lenses or cylindrical lenses can be selected and used for projecting the target. The optical system can also include, for example, an Alvarez lens system. In other words, the target (or the projected target or virtual target) is shown to the test subject, through which the test subject sees the target or virtual target. The optical system can also include, for example, two lenses that can rotate relative to each other, each lens having at least one cylindrical component in its effect. In particular, the optical system can have two cylindrical lenses that include rotationally symmetric surfaces facing each other and interlocking, preferably flat surfaces. The optical system can also include a positive cylindrical lens and a negative cylindrical lens with the same but opposite effects, which are rotatably supported relative to each other and preferably can be moved relative to each other.

[0360] Furthermore, when different effects are applied by means of the optical system, the viewing angle of the target may change. This can be prevented by a corresponding configuration of the optical system or can also be determined by calculation and compensated for during the showing. For this purpose, the viewing angle must be determined based on the applied effect, and a visual acuity value must be assigned based on this actual viewing angle, which can be achieved, for example, by determining the magnification of the optical system and a correspondingly reduced target display. Alternatively, the optical system can be calibrated with the aid of a camera, by means of which the size of the target can be directly determined using a camera arranged instead of at least one eye of the test subject (and observing the optical system).

[0361] In principle, the feedback on the test object or the test object's action can be implemented orally. In this case, the user can record the state of the optical system in the feedback or the test object's action and / or directly transmit the feedback to the feedback system. However, this variant is error-prone and causes delays. Therefore, direct feedback from the test object to the feedback system is preferred. For this purpose, in the simplest case, the feedback system can include a button. In another preferred embodiment, the feedback system can also include two buttons ("+" and "-"), three buttons ("+", "-", and "OK"), four buttons (e.g., "+", "-", "OK", and "Cancel"), etc., and / or can include a joystick. Alternatively or additionally, the feedback system can include a microphone for detecting the spoken words of the test object.

[0362] In an embodiment, the device includes an evaluation unit for determining the sensitivity of at least one eye of the test object based on at least two provided pairs of visual acuity-refractive values. Here, the visual acuity limit refraction determination unit can be a component of the evaluation unit. In other words, the evaluation unit can include the visual acuity limit refraction determination unit.

[0363] In another embodiment, the device includes an auto-refractor or aberrometer unit for determining one or more objective refractions of at least one eye of the test object, wherein the auto-refractor or chromatic aberration measurement unit is preferably designed to measure and / or monitor the accommodation state of at least one eye of the test object. In addition, the auto-refractor or aberrometer unit can include a camera for determining the pupil size (especially the pupil radius) of at least one eye of the test object as a refractive unit. Alternatively or additionally, the auto-refractor or aberrometer unit can include a calibration camera for calibrating the optical system. The camera for determining the pupil size and the calibration camera can also be implemented in a single camera that combines the two functions (determining the pupil size and calibrating the optical system).

[0364] In another preferred embodiment, the device includes a pupil size measurement unit (especially a camera) for determining the pupil size (especially the pupil radius) of at least one eye of the test object. Alternatively or additionally, the device can include an illumination device for generating at least two brightness levels. Alternatively or additionally, the device can include a pupillometer device that is designed to detect first pupil measurement data of at least one eye in a first brightness level and second pupil measurement data of at least one eye in a second brightness level.

[0365] On the other hand, there is provided a device for calculating, optimizing, or evaluating spectacle lenses for at least one eye of a test object taking into account the sensitivity of at least one eye of the test object, which includes a device for determining the sensitivity of at least one eye of a spectacle wearer according to the present invention.

[0366] Devices for calculating, optimizing or evaluating spectacle lenses may in particular comprise the following components:

[0367] - A surface model database for pre-setting a first surface and a second surface of a spectacle lens to be calculated or optimized;

[0368] - A principal ray extraction module for extracting the path of a principal ray passing through at least one view point of at least one surface of a spectacle lens to be calculated or optimized into a model eye;

[0369] - An evaluation module for evaluating the aberration of a wavefront generated by a spherical wavefront incident on the first surface of a spectacle lens along the principal ray at an evaluation surface, compared with the wavefront converging at a point on the retina of the eye model; and

[0370] - An optimization module for iteratively changing at least one surface of a spectacle lens to be calculated or optimized until the evaluated aberration corresponds to a pre-set target aberration.

[0371] On the other hand, there is provided a device for manufacturing a spectacle lens, comprising:

[0372] - A calculating or optimizing device designed to calculate or optimize a spectacle lens according to the method for calculating or optimizing a spectacle lens according to the invention; and

[0373] - A processing device designed to process a spectacle lens according to the result of the calculation or optimization.

[0374] On the other hand, there is provided a spectacle lens manufactured by the method for manufacturing a spectacle lens according to the invention and / or by means of the device for manufacturing a spectacle lens according to the invention.

[0375] Furthermore, the invention provides for the use of a spectacle lens manufactured according to the manufacturing method according to the invention, in particular in a preferred embodiment, in a pre-set average or customized use position in front of the eyes of a specific spectacle wearer, for correcting the visual defect of the spectacle wearer.

[0376] In particular, the computer-implemented method according to the invention can be provided in the form of off-the-shelf software and / or industrial software. In such a method, in particular, the data required for the calculation and / or optimization and / or manufacturing of spectacle lenses can be detected and / or transmitted.

[0377] The device and / or system according to the invention for ordering spectacle lenses, for example, may in particular comprise a computer and / or a data server, which are designed to communicate via a network (such as the Internet). According to the invention, the computer is in particular designed to execute a computer-implemented method, such as ordering software for ordering at least one spectacle lens, and / or transmission software for transmitting relevant data, and / or retrieval software for retrieving relevant data, and / or calculation or optimization software for calculating and / or optimizing the spectacle lens to be manufactured.

[0378] It is to be understood that, without departing from the scope of the invention, the features described above and those to be explained subsequently can be used not only in the respectively stated combinations, but also individually or in other combinations.

[0379] In the following, Figures 6 to 8 various embodiments for solving the task are described by way of example. Here, the various embodiments described sometimes have features that are not absolutely necessary for reproducing the claimed subject matter, but provide desired characteristics in certain applications. Therefore, embodiments that do not have all the features of the following embodiments should also be considered as disclosed in the described technical teaching. In addition, to avoid unnecessary repetition, only certain features are mentioned with respect to the various embodiments described below. It should be noted that the various embodiments should therefore be considered not only individually, but also in combination. By means of this combination, the person skilled in the art recognizes that the various embodiments can also be modified by combining single or multiple features of other embodiments. It should be noted that a systematic combination of single or multiple features of the various embodiments described with respect to other embodiments may be desirable and meaningful and should therefore be considered and also be regarded as included in the description.

[0380] Figure 6 An exemplary image or photograph is shown, which contains a hot air balloon and a road and conveys a sense of distance to the observer. Within the scope of the invention, such an image can, for example, be projected as a target (in particular as a virtual target) into at least one eye of a test subject in order to perform an objective refractive measurement, for example, in a blurred state in which the test subject only recognizes the image or image details as blurred.

[0381] Figure 7 Shows Figure 6An image or photograph having exemplary adapted visual markers integrated in or superimposed on the image for a selected preferred direction. Each of these adapted visual markers has a preset visual acuity or preset visual acuity level. Within the scope of the method according to the invention, the image with the adapted visual markers is provided with an adjustable target refraction by means of an optical system. The target refraction is changed by the optical system, and the test subject signals by means of a test subject action that the identifiability of the target or the adapted visual marker has changed at the time point of the test subject action. In this way, a visual acuity - refraction value pair can be provided in order to determine the sensitivity of at least one eye of the test subject.

[0382] One or more targets can be provided to the test subject or can be projected as virtual targets into at least one eye of the test subject. According to an embodiment, two or more targets can be used, and their content can also be the same.

[0383] The first target can for example be an image conveying a sense of distance (see for example Figure 6 ), the second target can be one or more adapted visual markers in a specific size, and the third target can be one or more adapted visual markers in a different size.

[0384] Alternatively, the first target can be an image conveying a sense of distance, while the second and third targets can be the same in content and can contain one or more adapted visual markers, each having one of two sizes.

[0385] Alternatively, all three targets can be the same and represent an image conveying a sense of distance, but contain one or more details, the recognition of which can be assigned to a visual acuity level respectively. These details are explicitly included in the description of the term "adapted visual marker". Examples of these details are in an image containing for example a hot air balloon and a road:

[0386] - Symbols or panels on the hot air balloon and the hot air balloon basket,

[0387] - Symbols in the clouds or clouds,

[0388] - Lines on the road, and / or

[0389] - Symbols on roadside signs.

[0390] Particularly suitable symbols for example have one or more concentric rings which merge into a circle in a given blur.

[0391] Differently from the prior art, in these embodiments, in order to obtain sensitivity, instead of obtaining the visual acuity level of a specific application effect, the application effect required to achieve a preset visual acuity is obtained. In addition, the obtaining of visual acuity can be associated with the measurement of autorefraction or aberration data in the unaccommodated state and the accommodated state. In a particular embodiment, the accommodation state of the eye can also be tracked in order to thereby obtain a more reliable sensitivity value.

[0392] A. Method according to an exemplary embodiment without subjective refraction

[0393] The examination of the test subject can be carried out, for example, as follows:

[0394] 1) By means of autorefraction or aberration measurement, determine the objective refractive value of the test subject. For this purpose, present a first target to the test subject. Here, through a suitable optical system, provide the test subject with a first effect that does not allow it to clearly identify the target completely, so as to thereby achieve relaxation of the ciliary muscle.

[0395] 2) Now, only provide the second target to the test subject, and apply a second effect by means of the optical system, in which the test subject with high visual acuity cannot recognize at least one adapted visual target. This is achieved in particular in such a way that a spherical effect is selected as the applied optical effect, which spherical effect corresponds to one of the two principal meridians of the mean spherical or target refractive value plus an additional positive optical effect. The latter effect (commonly referred to as "defocus") is thus selected because the test subject cannot compensate for this effect by accommodation. In order to determine the speed at which the provided optical effect changes, a standard value based on the average value of a plurality of test subjects can be used. For example, it is known that in defocus, visual acuity is approximately halved by 0.5 dpt spherical or 1 dpt cylindrical. Preferably, the target refraction changes as the applied optical effect at a speed between 1 / 16 dpt per second and 1 / 2 dpt per second. The additional optical effect may also depend on the pupil measured by the aberration measurement unit. It can, for example, be inversely proportional to the pupil radius, such that a test subject with a smaller pupil preferably has a stronger defocus effect than a test subject with a larger pupil, in order to ensure that the defocus perceived by all test subjects is similar.

[0396] 3) Alternatively, a spherical-cylindrical effect can also be provided as the optical effect. For example, the cylindrical effect of the optical system can be obtained from the objective refraction, and an additional positive spherical effect can be applied to the average objective refractive value. Alternatively or additionally, an astigmatic offset can be applied to the objective refractive value (so-called astigmatic defocus). Now, the optical effect slowly (for example, between 1 / 16 dpt per second and 1 / 2 dpt per second) changes along the best or objective refractive direction (by changing the spherical effect and / or changing the astigmatic effect).

[0397] 4) Once the test subject is able to recognize the pointing features of the adapted visual target of the second target by changing the applied optical effect, then it conveys this (e.g., by means of an "OK" button). If necessary, it can adjust the limiting effect itself (e.g., using the "+" and "-" buttons) and confirm the limiting effect (e.g., also by means of the "OK" button). Thus, when recognizing the second target, the effect adjusted here is stored as the "visual acuity limit effect" or the "visual acuity limit refraction".

[0398] 5) Provide the test subject with a third target.

[0399] 6) Now, the optical effect further changes slowly (e.g., between 1 / 16 dpt per second and 1 / 2 dpt per second) in the direction of the optimal or objective refractive value (by changing the applied optical effect).

[0400] 7) Once the test subject is able to recognize the pointing features of the adapted visual target of the third target by changing the applied optical effect, it conveys this (e.g., by means of an "OK" button). If necessary, it can adjust the limiting effect (e.g., using the "+" and "-" buttons) and confirm the limiting effect (e.g., also by means of the "OK" button). When recognizing the third target, the effect adjusted here is stored as the "visual acuity limit effect" or the "visual acuity limit refraction".

[0401] The sensitivity can be determined according to the visual acuity levels of the two targets, more precisely according to the two corresponding sizes of the pointing features of the two adapted visual targets, the objective refractive value, the optical effect applied when recognizing the second target, and the optical effect applied when recognizing the third target. For this purpose, in particular, sensitivity metrics can be used, as described above in the exemplary embodiments. Here, the false refraction is produced by the (e.g., spherical and / or astigmatic) distance between the optical effect applied when recognizing the respective target and the objective refractive value.

[0402] B. Method according to an exemplary embodiment with subjective refraction

[0403] In this variant, steps 5) to 7) above can be omitted from the method under section A. Thus, it is only necessary to determine the visual acuity of the target and the optical effect applied when recognizing the target (e.g., the pointing features of the target). Subsequently, subjective refraction determination is performed, and the subjective refractive value and visual acuity (visual acuity cum correctione, VCC) achieved by the test subject are determined thereby. The objective refractive value can be used here as the starting value for determining the subjective refraction.

[0404] Alternatively, subjective refraction and visual acuity determination can be performed before the steps from section A. In this case, performing autorefraction or aberration measurement can be omitted, and determining the objective refractive value (step 1) can be omitted, and the subjective refractive value can be used at this point.

[0405] Here, the refractive error can be calculated as the spherical distance or the astigmatic distance of the effect when recognizing the target from the subjective refractive value.

[0406] Instead of the subjective refractive value, a combined refractive value can also be used to calculate the sensitivity or the refractive error. This can be calculated based on the subjective refractive value and the objective refractive value or additional data (such as low-order or high-order aberrations from an aberrometer or other biometric data, such as corneal shape, distance between the lens and the retina, anterior chamber depth).

[0407] C. Adapt the visual acuity level of the target

[0408] In addition, at least one visual acuity level of an adapted target or multiple adapted targets can be adapted to the test subject. For example, this is useful if the astigmatism of the test subject cannot be compensated. Subsequently, the visual acuity level of the (virtual) target can be selected such that the target can still be recognized despite the refractive error due to astigmatism.

[0409] Information about the visual acuity (e.g., visual acuity with a corrective device or without a corrective device, e.g., from subjective refraction determination) can be fed into the determination of the target size, i.e., the size of the pointing feature of the adapted target of the target.

[0410] If the test subject does not recognize the pointing feature of the adapted target despite a small deviation of the applied optical effect from the objective, subjective, or combined refractive value, then the visual acuity level can be switched to a lower level, and the corresponding steps can be repeated at the lower visual acuity level.

[0411] Additionally or alternatively, the findings from step 4 can be included in the determination of the visual acuity level in step 6.

[0412] To prevent the test subject from already recognizing the adapted target during multiple measurements or when switching between eyes, at least one adapted target or symbol or detail in the image may change between different measurements or when switching between eyes. In particular here, the selected preferred direction can be adapted to the astigmatism of the other eye, or the adapted Landolt ring can be switched to the adapted Snellen - E. For this purpose, an electronic display is of course particularly suitable as a target providing device.

[0413] D. Find the defocus and have the test subject adjust the effect

[0414] Find the out-of-focus point

[0415] As an alternative to the method in the above section, the optical effect provided according to section A or B) at the start (i.e., step 2) can also be an effect that allows the recognition of the pointing features of an adapted visual target. This can be an objective, subjective, or combined refractive value.

[0416] In steps 5) and 6), the provided optical effect is then removed from this optical effect in the positive direction. The direction is chosen to prevent adaptation. In steps 4) and 7), the test subject then signals the time point at which it can no longer recognize the pointing features of the visual target.

[0417] If, similar to the method in section A, the applied optical effect is determined for two visual acuity levels, then in this case the applied optical effect can first be determined for the higher visual acuity (steps 2 - 4), and subsequently for the lower visual acuity (steps 5 - 7). Thus, during the method, the refractive error may increase, whereby the pointing features of the adapted visual target with more difficult recognizability (higher visual acuity level) and then with easier recognizability (lower visual acuity level) first become unrecognizable.

[0418] Correct the focus point (out-of-focus point)

[0419] In steps 4) and 7) of the above embodiment, if the test subject is unsure that it has signaled the correct time point or the correct provided optical effect, then it can optionally correct the provided (i.e., applied) optical effect. This can be done, for example, with the "+" and "-" buttons of a feedback unit.

[0420] Adjust the focus point (out-of-focus point) by the test subject

[0421] The test subject can also be directly asked to adjust the provided optical effect in which it can still or no longer recognize the pointing features of the adapted visual target. For example, this can be done with the "+" and "-" buttons of a feedback unit.

[0422] Approach the focus point (out-of-focus point) from different directions

[0423] Furthermore, one defocus point can be determined when increasing, and another defocus point can be determined when decreasing. These points may be different from each other and are then averaged. Alternatively, within the range of minimizing the squared error, the sensitivity can be determined from the two defocus points with the aid of known metrics.

[0424] Repeat the measurement

[0425] Of course, the determination of defocus can also be carried out multiple times to improve the measurement accuracy of the method.

[0426] Monitor the adjustment status

[0427] During steps 3), 4), 6) or 7) of the method according to section A, or during steps 3) or 4) of the method according to section B, the accommodation state of at least one eye of the test subject can be monitored by means of an auto-refractor or aberrometer unit. The results obtained thereby can be used to control the progression (for example, to terminate or repeat individual steps in the case of an undesired accommodation (for example, exceeding a certain threshold)). The measurement can be carried out not only continuously but also only when a signal of recognizability is issued.

[0428] Furthermore, the accommodation state (spherical aberration, cylindrical aberration, low-order aberration or high-order aberration), which is ideally measured when a signal of recognizability is issued, can be included in the calculation of sensitivity or refractive error.

[0429] E. Defocus in the negative direction and combined with myopia measurement

[0430] Blurriness in the negative direction

[0431] In the above-described embodiments, the applied optical effect corresponds to a refractive error in the positive direction, since this cannot be compensated by the test subject by accommodation. However, the opposite case can also be achieved, i.e., an applied optical effect corresponding to a refractive error in the negative direction. The accommodation that may occur here can be handled as follows:

[0432] - Disregard accommodation;

[0433] - Measure test subjects who are, for example, physiologically (e.g., in an age-related manner) or pharmacologically (e.g., by drops) affected or can only accommodate to a very poor extent;

[0434] - Measure or monitor the accommodation state;

[0435] - Use an assumption about the accommodation ability (for example, age-based according to the Duane curve, see Figure 3).

[0436] Figure 8The Duane curve shown is from B. Lachenmayr, D. Friedburg, E. Hartmann, A. Buser: “Auge - Brille - Refraktion: Schober - Kurs: verstehen - lernen - anwenden” [Eye - Glasses - Refraction: Schober Course: Understand - Learn - Apply], 2005, Figure 1.29, originally published in Alexander Duane: “Studies on monocular and binocular accommodation and their clinical applications”, Transactions of the American Ophthalmological Society, Vol. 20, 1922, pp. 132 - 157, PMID 16692582, PMC 1318318. The Duane curve shows that the accommodation ability (amplitude of accommodation) of the human eye decreases continuously from 8 years old to just over 50 years old, on average from 14 diopters to 1 diopter.

[0437] The influence of accommodation on the sphere can be considered here, for example, in the following way:

[0438] - The accommodation value is the refractive value for hyperopia minus the distance value of the application effect;

[0439] - The refractive error is calculated directly from the application effect and the measured or assumed refractive value.

[0440] In a similar way, the astigmatism deviation can also be calculated based on the measured cylinder with known forms (such as the crossed - cylinder formula, power - vector notation) in order to take into account the astigmatism changes due to accommodation. In addition, the measured higher - order aberrations can be taken into account by known metrics.

[0441] Combine myopia measurement

[0442] The above - mentioned methods can be combined with the determination of the objective myopic refractive value, maximum accommodation, and / or (low - order or high - order) aberrations.

[0443] To this end, the following can be done: Monitor the accommodation state of the eye using autorefraction or aberration measurement (ideally simultaneously and as frequently as possible). Start with the applied optical effect, which allows the pointing characteristics of the adapted test target to be identified. This can be objective, subjective, or combined refractive values. In step 5) and possibly step 6), the provided optical effect is subsequently removed from this optical effect in the positive direction. In step 4) and possibly step 7), the test subject then signals the time point at which it can no longer identify the pointing characteristics of the adapted test target. If the application effect is determined for two visual acuity levels, then in this case, the application effect can first be determined (steps 2 - 4) for the higher visual acuity and subsequently (steps 5 - 7) for the lower visual acuity. Thus, during the method process, the refractive error may increase, whereby the adapted test target with more difficult recognizability (higher visual acuity level) and then the adapted test target with easier recognizability (lower visual acuity level) first become unrecognizable. The autorefraction or aberration values measured when the loss of recognizability is signaled (correspondingly) are used to calculate the sensitivity or visual acuity.

[0444] Subsequently, the autorefraction or aberration value corresponding to the maximum accommodation is used as the value of the myopic refractive error or the maximum accommodation ability (spherical aberration, cylindrical aberration, low - order aberration, or high - order aberration).

[0445] F. Monitor the pupil size

[0446] In addition, the pupil size (e.g., as the pupil radius) can be monitored, for example, by a camera arranged in the autorefractor or aberrometer or by a separate camera. The pupil size measured at the defocus point or correspondingly shortly before the defocus point (e.g., at most 2 seconds before reaching the defocus point) can be used to determine the sensitivity to blur.

[0447] Subsequently, the measured pupil size can be used to quantify the blur of the image on the retina with the aid of a suitably parameterized eye model and known additional blur. For example, the angle can be calculated: in this angle, the circle of confusion of a point shown blurred can be observed in a given pupil and given additional blur (see WO 2019034525A1). The sensitivity can be determined within the scope of this visual acuity model as the deterioration of visual sharpness per circle of confusion angle.

[0448] G. More complex sensitivity models

[0449] In a more complex model, the effects of spherical blur or refractive error and astigmatic blur or refractive error can be distinguished. To this end, for the same visual acuity level, the spherical blur and the astigmatic blur can be determined.

[0450] I. Combination with other measurements

[0451] The present invention can be combined well with other measurements or incorporated into other measurements. In a preferred embodiment, the method according to section A or section B is performed after an autorefraction or aberration measurement for hyperopia. Here, such an autorefraction or aberration measurement for hyperopia already represents the first step according to section A and does not have to be performed again. Here, the method according to one of the above sections can be performed before or after a possible myopia measurement. The advantage of the first method is that the (virtual) target is still unknown to the test subject at first, and the test subject is already familiar with the target for myopia measurement.

[0452] List of reference signs

[0453] V1 First preferred direction

[0454] V2 Second preferred direction

Claims

1. A method for determining the visual acuity characteristics of a test subject having at least one astigmatic vision defect, comprising the following steps: - Providing vision defect data of the test subject, wherein the vision defect data contains at least one axis position of the required optical cylindrical correction; - Selecting a preferred direction (V1; V2) such that the preferred direction (V1; V2) either corresponds to the axis position assigned to the optical cylindrical correction, or is rotated 90° relative to the axis position, or the preferred direction (V1; V2) is derived from wavefront data by a point spread function; - Applying an optical effect at least in the selected preferred direction; - Presenting at least one adapted visual target having a pointing feature, wherein the adapted visual target is presented in an oriented manner such that the pointing feature of the adapted visual target is arranged parallel to the preferred direction (V1; V2); and - Determining the visual acuity characteristics of the test subject for the selected preferred direction (V1; V2) taking into account at least one dimension of the pointing feature of the adapted visual target and the applied optical effect.

2. The method according to claim 1, wherein The pointing feature of the adapted visual target has a sequence of bright and dark regions following each other along the preferred direction (V1; V2).

3. The method according to claim 1 or 2, having the following steps: - Providing an unadapted standard visual target having a pointing feature; - Rotating the standard visual target in a display plane such that the pointing feature of the standard visual target is arranged parallel to the preferred direction (V1; V2); and - Presenting the so-rotated standard visual target as the adapted visual target.

4. The method according to any one of the preceding claims, wherein: - As a first preferred direction (V1), an axis position assigned to the optical cylindrical correction and arranged in the first principal meridian of the required optical cylindrical correction is selected, wherein an optical spherical correction is applied as the optical effect, which corrects the vision defect of the test subject in the first principal meridian according to the vision defect data, and wherein the visual acuity of the test subject for the first principal meridian is determined as the visual acuity characteristic, and / or - As a second preferred direction (V2), a direction rotated 90° relative to the axis position, which is arranged in the second principal meridian of the required optical cylindrical correction, is selected, wherein an optical spherical correction is applied as the optical effect, which corrects the vision defect of the test subject in the second principal meridian according to the vision defect data, and wherein the visual acuity of the test subject for the second principal meridian is determined as the visual acuity characteristic.

5. The method according to claim 4, wherein The visual acuity of the test subject is determined for the first principal meridian and the second principal meridian of the required optical cylindrical correction, and an orientation-independent visual acuity is derived therefrom.

6. The method according to any one of the preceding claims, wherein, Using a Landolt ring as the adapted visual target, the notch of the Landolt ring is presented as being rotated 90° relative to the selected preferred direction (V1; V2).

7. The method according to any one of the preceding claims, wherein, The Snellen-E is used as an adapted visual target, in the case of the Snellen-E, the connecting lines connecting three parallel E-lines are arranged parallel to the selected preferred direction (V1; V2).

8. The method according to claim 6 or 7, wherein the adapted visual target is shown rotated clockwise by 90° at least once and rotated counterclockwise by 90° at least once relative to the preferred direction (V1; V2), and wherein within the scope of the visual task, the test subject is required to distinguish between these two differently rotated adapted visual targets from each other.

9. The method according to any one of the preceding claims, wherein A shaded surface is used as an adapted visual target, in the case of the shaded surface, the hatching lines are arranged perpendicular to the selected preferred direction (V1; V2).

10. The method according to any one of the preceding claims, wherein, At least one additional visual target is shown in addition to the adapted visual target, the gray value of the additional visual target roughly corresponds to the average gray value of the adapted visual target, and within the scope of the visual task, the test subject is required to distinguish between the shown visual targets from each other.

11. The method according to any one of the preceding claims, wherein, The applied optical effect is varied at least until the limiting refraction for the selected preferred direction, and the test subject recognizes the pointing feature of the adapted visual target starting from the preferred direction.

12. The method according to any one of claims 1 to 10, wherein The size of the pointing feature of the adapted visual target is varied at least until a limiting size, and the test subject recognizes the pointing feature of the adapted visual target up to the limiting size.

13. The method according to any one of the preceding claims, wherein, At least one visual acuity and / or at least one sensitivity and / or at least one visual acuity - refraction - value pair and / or at least one refraction value are determined as a visual sharpness characteristic.

14. The method according to any one of the preceding claims, wherein, At least one visual task depending on the shown adapted visual target is provided to the test subject, and the test subject responds to the visual task with active and / or passive feedback.

15. The method according to any one of the preceding claims, wherein, When the two applied optical effects are different, the visual acuity of the test subject in the selected preferred direction (V1; V2) is determined, and therefrom the sensitivity of the test subject is determined.

16. The method according to any one of the preceding claims, wherein, Subjective and / or objective refraction is performed, and the vision defect data of the test subject are derived from the vision defects obtained thereby for the test subject.

17. The method according to any one of the preceding claims, wherein, The visual acuity of the test subject is determined as a visual sharpness characteristic and is converted into a different type of visual acuity from the visual sharpness characteristic.

18. The method according to any one of the preceding claims, wherein, At least one of the adapted visual targets is shown clearly visible for the test subject without correction and / or without full correction of the optical cylindrical correction required for the test subject.

19. Use of an adapted optotype, the adapted optotypes having respectively pointing features arranged parallel to a preferred direction (V1; V2), the preferred direction corresponding either to the axis position assigned to the required optical cylindrical correction of the test subject or being rotated by 90° relative to said axis position, or the preferred direction (V1; V2) being derived from wavefront data by means of a point spread function, in order to determine the visual acuity characteristics of the test subject for the selected preferred direction (V1; V2), taking into account at least one dimension of the pointing feature of the adapted optotype.

20. A device for determining the visual acuity characteristics of a test subject having at least one astigmatic visual defect, comprising: - a selection module which selects a preferred direction, where the preferred direction (V1; V2) corresponds either to the axis position assigned to the required optical cylindrical correction of the test subject or is rotated by 90° relative to said axis position, or the preferred direction (V1; V2) is derived from wavefront data by means of a point spread function; - a refractive unit configured to apply an optical effect to the test subject in the selected preferred direction; - a display module having a display, the display module showing on the display at least one adapted optotype having a pointing feature such that the pointing feature of the adapted optotype is arranged parallel to the preferred direction (V1; V2); and - a visual acuity characteristics determination module which determines the visual acuity characteristics of the test subject for the selected preferred direction (V1; V2), taking into account at least one dimension of the pointing feature of the adapted optotype and the applied optical effect.

21. The device according to claim 20, comprising an eye tracking unit which tracks at least one eye of the test subject when showing at least one adapted optotype.

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