Determination of incorrect eye refraction

Abstract

The present invention relates to a method (210), an apparatus (110) and a computer program for determining the refractive error of at least one eye (112) of a user (114), and to a method for manufacturing spectacle lenses for at least one eye (112) of a user (114). The method (210) for determining the refractive error of at least one eye (112) of a user (114) comprises the steps of: a) presenting at least one symbol (122) on a visual display unit (120), wherein at least one parameter of the at least one symbol (122) presented on the visual display unit (120) is variable; b) acquiring an eye movement metric (144) of at least one eye (112) of the user (114) based on the at least one symbol (122) presented on the visual display unit (120); c) establishing a time point at which a recognition threshold of the user (114) for the at least one symbol (122) presented on the visual display unit (120) is evident from the eye movement metric (144) of at least one eye (112) of the user (114); and d) determining the value (220) of the refractive error of at least one eye (112) of the user (114) according to the at least one parameter established at this time point. The present invention allows the value (220) of the refractive error of at least one eye (112) of a user (114) to be objectively determined without using dedicated equipment and without feedback from the user (114), which is position-independent and suitable for use by an ordinary person.

Description

Technical Field

[0001] The present invention relates to a method, an apparatus and a computer program for determining the refractive error of at least one eye of a user, and a method for manufacturing spectacle lenses for at least one eye of a user. Background Art

[0002] The prior art has disclosed methods for determining the refractive error of a user's eye. Herein, the term "refraction" refers to the refraction of light experienced by a light beam incident through the pupil into the interior of the eye in the user's eye. Defocusing of the user's eye (i.e., a specific refractive error) causes refractive errors (ametropias) of the user, in particular myopia (nearsightedness) or hyperopia (farsightedness) of the user. To subjectively determine refraction, optotypes, preferably in the form of numbers, letters or symbols, are typically provided on a board or a visual display unit having a defined size for a given distance and observed by the user. By providing a plurality of optical lenses with known characteristics and by guiding the user through a questionnaire process, the defocus of the user's eye can be subjectively determined and it can be determined which spherocylindrical configuration of, for example, spectacle lenses produces a substantial compensation for the refractive error of the eye and thus optimizes the image quality as much as possible for the user.

[0003] Furthermore, known methods for objectively determining eye refraction require an optical measuring instrument configured for this purpose, and the light source required for this purpose is aligned with the optical axis of the eye. Therefore, known devices for objectively determining refraction can generally only be operated by professionals, in particular opticians, and are generally stationary and thus cannot be used in a mobile environment.

[0004] US 2012 / 019779 A1 discloses a method for acquiring visual function, the method comprising: stimulating optokinetic nystagmus by presenting a visual stimulus to a user; changing a first parameter of the visual stimulus; changing a second parameter of the visual stimulus; and using the changed visual stimulus to determine a threshold stimulus for optokinetic nystagmus, wherein the first parameter and the second parameter are selected from a group of parameters comprising: the pattern of the visual stimulus, the width of the visual stimulus, the distance between the visual stimulus and the patient, the spatial frequency of the visual stimulus, the rate of change or temporal frequency of the test surface of the visual stimulus, and the contrast between elements of the visual stimulus.

[0005] US 2013 / 176534 A1 discloses a method for adaptively determining a model of a user's visual performance, in which the user undergoes multiple tests. Each test includes: identifying a stimulus pattern; generating a pattern on a display, determining whether the pattern produces optokinetic nystagmus, updating the model to include the results of the optokinetic nystagmus examination, and determining whether the updated model is acceptable. These tests can be repeatedly repeated until the visual performance model of the user is acceptable.

[0006] US 2014 / 268060 A1 discloses an apparatus and method for determining the refraction and astigmatism of an eye using a computer vision display unit. For this purpose, a test target is displayed on the visual display unit, and the value of the test target size when the test target can no longer be distinguished by the user is established by changing the size of the test target displayed on the visual display unit.

[0007] EP 1 948 002 A1 discloses a method for testing a person's eyesight. For this purpose, the person needs to identify a target symbol in one or more sequences of test images and activate an activation controller. A parameter value is obtained by processing the activation information, and this parameter value can then be assigned to a visual metric.

[0008] WO 2018 / 077690 A1 discloses an apparatus and a computer program that can be used to determine the spherocylindrical refraction of an eye. For this purpose, a component with an adjustable optical unit is provided, and the optical unit can be adjusted in terms of its refractive power by means of a refractive power setting device. Then, the refractive power setting device is set at different orientations of the preferred direction of the optical unit or the preferred direction of the test target to determine the spherocylindrical refraction.

[0009] In addition, methods and devices for determining the eye movements of a user are known.

[0010] US 6,402,320 B1 discloses an automatic method for determining the visual acuity of a user, particularly an infant, through an electronic visual display device, the method comprising the following method steps: (a) providing a fixation target on the display device as a stimulus to the user; then (b) providing a test image on the display device, wherein the test image includes at least two separate fields, wherein one field has a first test pattern and the other field has a control pattern, wherein the test pattern is configured to become a stimulus to the user once the test pattern can be distinguished by the user; then (c) detecting whether an eye movement towards the test pattern has occurred, the presence of an eye movement towards the test pattern confirms the user's ability to identify the first test pattern; and (d) repeating steps (b) and (c) with additional test patterns that are more difficult to identify than the first test pattern; and (e) determining the visual acuity of the user from the occurrence or non-occurrence of eye movements towards the first test pattern and at least one additional test pattern.

[0011] Rucci, M., Iovin, R, Poletti, M., and Santini, F (2007) reported in " Miniature eye movements enhance fine spatialdetail / [Enhanced fine spatial detail from microsaccadic eye movements]" (Nature, 447 (7146), p. 852) an analysis of the effect of fixational eye movements on the discrimination of gratings masked by noise having a power spectrum similar to that of natural images. By a method for stabilizing the retinal image, the movement of the retinal image that occurs between successive jumps (called saccades) of the eye movement used to acquire a new fixation point can be selectively eliminated. This publication states that fixational eye movements can improve the ability to discriminate high-spatial-frequency stimuli, but not low-spatial-frequency stimuli. This improvement stems from the temporal modulation introduced by fixational eye movements in the visual input to the retina, which emphasizes high-spatial-frequency stimuli. In natural vision dominated by low-spatial-frequency stimuli, fixational eye movements appear to represent an effective strategy for processing spatial detail.

[0012] US 2015 / 070273 A1 discloses methods and devices for optically detecting and tracking eye movements. A method for tracking eye movements includes: emitting light to a user's eye using a plurality of light sources that are substantially equidistant from a photodetector module of the device; receiving at the photodetector module at least a portion of the light retroreflected from each of the plurality of light sources that is retroreflected from the eye; and determining a position parameter of the eye based on different values of at least a portion of the light retroreflected related to the plurality of light sources.

[0013] Denniss, J., Scholes, C., McGraw, P. V., Nam, S. H., and Roach, N. W. (2018) described in " Estimation of Contrast Sensitivity From Fixational Eye Movements / [Estimating contrast sensitivity from fixational eye movements]" (Investigative Ophthalmology & Visual Science, 59 (13), pp. 5408-16) a method for objectively and reliably estimating contrast sensitivity from the observation of microsaccades. The results obtained therefrom indicate that as the image contrast increases, the microsaccade rate likewise increases. SUMMARY OF THE INVENTION

[0014] Starting from the disclosures of US 2012 / 019779 A1 or US 2013 / 176534 A1, in particular, the object of the present invention is to provide a method, device and computer program for determining the refractive error of at least one eye of a user, as well as a method for manufacturing spectacle lenses for at least one eye of a user, which at least partially overcome the existing disadvantages and limitations of the prior art.

[0015] In particular, the method, device and computer program should assist in determining the refractive error of at least one eye without having to resort to the subjective responses of the user. In this case, the refractive error of at least one eye of the user will be determined without professional equipment and should therefore also be able to be carried out by non-professionals.

[0016] This object is achieved by a method, device and computer program for determining the refractive error of at least one eye of a user, as well as a method for manufacturing spectacle lenses for at least one eye of a user, which have the features of the independent claims. Preferred configurations that can be implemented individually or in combination are given in the dependent claims.

[0017] Hereinafter, the terms "show", "have", "include" or "contain" or any grammatical deviation thereof are used in a non-exclusive manner. Accordingly, these terms can refer to a situation where no other features exist in addition to the features introduced by these terms, or a situation where one or more other features exist. For example, the expressions "A shows B", "A has B", "A includes B" or "A contains B" can refer to a situation where no other elements are provided in A except B (i.e., the situation where A consists only of B), and a situation where, in addition to B, one or more other elements are provided in A, such as element C, elements C and D, or even other elements.

[0018] In a first aspect, the present invention relates to a method for determining the refractive error of at least one eye of a user. In this case, the method can relate to determining the refractive error of one eye or both eyes of the user. The method comprises the following steps a) to d) preferably in the stated order. In principle, another order is also possible. In particular, these steps can also be carried out in whole or in part simultaneously. The individual, multiple or all steps of the method can also be carried out repeatedly, in particular more than once. In addition to the stated steps, the method can also include additional method steps.

[0019] A method for determining the refractive error of at least one eye of a user comprises the following steps:

[0020] a) Represent at least one symbol on a visual display unit, wherein at least one parameter of the at least one symbol represented on the visual display unit is variable;

[0021] b) Acquire an eye movement metric of at least one eye of a user based on the at least one symbol represented on the visual display unit;

[0022] c) Establish a time point at which a recognition threshold of the user for the at least one symbol represented on the visual display unit is apparent from the eye movement metric of at least one eye of the user; and

[0023] d) Determine a value of the refractive error of at least one eye of the user based on the parameter defined at the time point.

[0024] The method for determining the refractive error of at least one eye of a user proposed herein is particularly applicable to a method for manufacturing spectacle lenses for at least one eye of a relevant user. According to Sections 8.1.1 and 8.1.2 of the standard DIN EN ISO 13666:2013-10 (hereinafter also referred to as the "standard"), "spectacle lens" shall be understood to mean the following ophthalmic lenses: within the scope of the present invention, the ophthalmic lens shall be used to correct the refractive error of the eye, and the ophthalmic lens is worn in front of the user's eye but does not contact the eye.

[0025] In the context of the present invention, the term "spectacles" denotes any element comprising two separate spectacle lenses and a spectacle frame, and the spectacle lenses are arranged to be inserted into a spectacle frame selected by the user of the spectacles. Instead of the term "wearer" used herein, one of the terms "subject", "spectacle wearer", "user" or "subject" may also be used synonymously.

[0026] According to step a) of the present method, at least one symbol is presented on a visual display unit, wherein at least one parameter of the at least one symbol presented on the visual display unit is variable. Here, the term "visual display unit" refers to any electrically controllable display having a two-dimensional extent, and at any position within this extent, corresponding desired symbols can be presented with largely freely selectable parameters. In this case, the visual display unit can preferably be selected from a monitor, a screen or a display. In this case, the visual display unit can preferably be included in a mobile communication device. In this case, the term "mobile communication device" particularly includes a cellular phone (mobile phone), a smart phone or a tablet computer. However, other types of mobile communication devices are conceivable. Thus, the present method for determining the refractive error of at least one eye can be performed at any desired location. However, other types of visual display units are also possible.

[0027] In this case, the term "symbol" relates to at least one visual mark, in particular a letter, a digit or a logo; at least one image or at least one pattern that can be represented in color or in black and white. Although the "visual marks" are respectively separate fixed symbols that can only vary limitedly in their proportions for recognition by the user, the term "pattern" represents any graphic structure, in particular compared to noise without a recognizable structure, the graphic structure has at least one spatially oriented period within which the pattern is repeatedly represented. Therefore, in order to clearly express this characteristic of the pattern, the term "periodic pattern" is also used instead of the term "pattern". However, these two terms should have the same connotation below.

[0028] In a preferred configuration, at least one symbol can be presented over the extent of the visual display unit such that the orientation relative to at least one symbol (e.g., the edge of at least one symbol) can adopt a fixed angle relative to the orientation of the visual display unit, and this fixed angle is preferably a multiple of 0° or 90°. In this case, the term "orientation" represents a direction preferably parallel to the edge of the visual display unit which generally has a rectangular shape. In this way, at least one symbol can be adapted to the extent of the current visual display unit. However, other ways of presenting at least one symbol on the visual display unit can be envisaged, such as a fixed angle of 45° or an odd multiple thereof relative to the orientation of the visual display unit.

[0029] Due to electronic control, at least one parameter of at least one symbol represented on the visual display unit can be easily varied within a wide range. A "parameter" is a characteristic of at least one symbol, depending on the selected symbol, in particular extent, orientation, frequency, contrast or color (including black and white). In the case of at least one pattern, the structure can be repeatedly represented, and due to the repetition, similarity points or regions can be formed on the structure of at least one pattern. The preferred configuration of the similarity points or regions can preferably be presented as the periodic maxima or minima of at least one pattern. Although at least one selected parameter of at least one conventional visual mark (in particular a letter, a digit or a symbol) can thus be the extent of at least one visual mark (in particular height or width), in the case of at least one periodic pattern, this at least one parameter is preferably related to at least one parameter of at least one periodic function (in particular at least one repetition frequency). In this case, a "periodic function" represents an instruction for configuring a temporally repeated or preferably spatially repeated variation of at least one pattern. The periodic function can preferably be selected from a sine function, a cosine function or their superposition. However, other periodic functions can be envisaged.

[0030] In a particularly preferred configuration of the present invention, at least one symbol represented on the visual display unit can move on the visual display unit. In this case, the movement of at least one symbol represented on the visual display unit can be implemented in a continuous manner or in a jumping manner. In this case, the term "movement" means a change in the position of at least one symbol representation on the visual display unit over time, regardless of whether at least one symbol represented on the visual display unit changes due to its parameterization during the movement process. However, according to the present invention, it is particularly preferred that at least one parameter of at least one symbol represented on the visual display unit is changed when at least one symbol represented on the visual display unit moves on the visual display unit. In this context, it is irrelevant that the movement of at least one symbol on the visual display unit is merely virtual. Due to electronic actuation, the position of the representation of at least one symbol on the visual display unit can be changed in such a simple way that the change can be implemented in a way that is faster than the user can perceive, and thus the user can assume that at least one symbol actually moves on the visual display unit. Generally, in this case, if the position of the representation of at least one symbol on the visual display unit changes correspondingly slowly, the user can recognize continuous movement. Then similarly, a rapid or significant spatial change in the position of the representation of at least one symbol on the visual display unit may cause the user to think that at least one symbol jumps on the visual display unit.

[0031] In a preferred configuration, at least one symbol represented on the visual display unit can be at least one pattern, wherein at least one parameter associated with the at least one pattern includes at least one spatial frequency of the periodic pattern. In this case, the term "spatial frequency" means the reciprocal of the spatial distance between two adjacent arranged similar points (especially the maximum point value or the minimum point) in the spatial periodic change of at least one pattern, and it can be specified in units of 1 / m, or particularly, if the distance between the visual display unit and the user's eyes is known, it can alternatively or additionally be specified as a dimensionless number such as per degree or per cycle. In this case, the intensity or color of at least one pattern can preferably follow a curve of a periodic function (especially a sine function) along one extension direction of the visual display unit. However, other ways of determining the spatial frequency according to at least one pattern are conceivable, for example, according to the spacing of equal-intensity points.

[0032] In this preferred configuration, at least one pattern or at least one periodic pattern can be designed as a two-dimensional superposition of periodic functions (in particular, sine functions and constant functions), where the sine function can extend in a first direction along the extent of the visual display unit, the constant function can extend in a second direction along the extent of the visual display unit, and the second direction can preferably be arranged perpendicular to the first direction. In this case, the term "perpendicular" means an angle of 90° ± 30°, preferably 90° ± 15°, particularly preferably 90° ± 5°, and especially 90° ± 1°. However, other angles between the first direction and the second direction are also possible. In this way, at least one pattern can exist in the form of stripes arranged adjacent to each other in a periodic manner, and these stripes can also be referred to as "sinusoidal gratings" or "Gabor patches". The term "Gabor patch" refers to a sinusoidal grating that is typically provided with a Gaussian envelope and is known to be particularly useful as a stimulus for at least one eye of the user. However, other types of patterns are also possible.

[0033] According to step b), preferably, during the representation of at least one symbol on the visual display unit in accordance with step a) and based on at least one symbol represented on the visual display unit and used as a stimulus for at least one eye of the user, an eye movement metric of at least one eye of the user is acquired. In this case, the term "eye movement metric" refers to a metric associated with the movement of at least one eye of the user, where the movement of at least one eye of the user is caused by an external stimulus acting on at least one eye of the user. Within the scope of the present invention, the eye movement metric can preferably relate to: eye pursuit movement; eye movements related to microsaccades and including microsaccade direction, microsaccade rate, and / or saccade accuracy; or optokinetic nystagmus. Additional eye movement metrics can, for example, include the dwell time when at least one represented symbol is read smoothly, which is also referred to as "fixation duration". Moreover, other types of eye movements can also be acquired. Which type of eye movement metric or which combination of at least two eye movements is used to determine the value of the refractive error of at least one eye of the user, particularly to determine the contrast sensitivity at the spatial frequency of at least one pattern (as described in more detail below), basically depends on the accuracy of the camera used for this purpose.

[0034] In this case, the term "eye pursuit movement" denotes the movement of at least one eye, which uses this movement to pursue the movement of at least one symbol represented on a visual display unit and gazed upon by at least one eye. Generally, the eye pursuit movement is a slow movement of at least one eye with an angular velocity of from 0.5° / s to 50° / s, during which the image representation of at least one symbol is preferably retained on the fovea of at least one eye. The eye pursuit movement cannot be generated automatically, but requires at least one symbol represented on the visual display unit to perform a movement that the at least one eye of the user can track.

[0035] Within the scope of the present invention, eye movement metrics based on saccades or microsaccades can preferably be used as a measure for establishing whether the user has recognized at least one symbol represented on the visual display unit as a stimulus. The term "saccade" denotes jerky visual target movements of at least one eye of the user, which are performed in a target-related manner and have a small amplitude of at least 1°, and are particularly used for the purpose of quickly and regularly realigning the line of sight of at least one eye at the fixation point, preferably by means of the image representation of at least one symbol located at the fixation point being displaced from the periphery to the fovea of at least one eye. The "saccade rate" is generally from 1 Hz to 5 Hz, where an angular velocity of from 5° / s to 500° / s can be achieved. The term "microsaccade" denotes tiny jerky and involuntary visual movements, which may be unrelated to the target, occur randomly, and have an amplitude of less than 1°. The "microsaccade direction" relates to the spatial orientation of the microsaccade with respect to a coordinate system, which is preferably a coordinate system established by the visual display unit. In this case, the orientation with respect to at least one symbol represented on the visual display unit can be used as a measure for recognition. The "saccade accuracy" denotes the spatial accuracy of the realignment with respect to the new position of the stimulus. If the perception of the stimulus after realignment is poor, then in this case, the expected error of readjustment is greater.

[0036] As an alternative or in addition thereto, eye movement metrics related to optokinetic nystagmus can preferably be used as a measure for establishing whether the user has recognized at least one symbol represented on the visual display unit as a stimulus. The term "optokinetic nystagmus" denotes a physiological eye movement reflex characterized by slow and fast phases. In this case, the slow phase corresponds to a pursuit movement at the speed of a moving stimulus in the surrounding environment. The correlation of the phase or speed of the stimulus on the visual display unit with the slow phase of the optokinetic nystagmus can be used as a measure for whether the user has recognized the stimulus.

[0037] In this case, in order to collect eye movement metrics, a camera can preferably be used, particularly in order to be able to perform video-based "eye tracking". In this case, the term "camera" denotes a camera that is configured to record an image sequence of the eye region of the user. The eye region preferably includes at least one eye of the user, and particularly preferably both eyes. At least one observed eye movement metric can be evaluated by image processing based on the image sequence of the eye region recorded by the camera, preferably in an evaluation unit configured for this purpose. For this purpose, known algorithms can be used specifically respectively.

[0038] Moreover, image processing in the evaluation unit can also preferably be used to determine other geometric data (particularly the position and diameter of the pupil) of at least one eye (preferably its pupil) from the image sequence recorded by the camera, and thereby, for example, the line of sight of at least one eye can be determined. In addition, if at least one eye is illuminated by a light source, a method including selected reflection points occurring on the front side and / or the back side of the cornea and the lens can be used. In particular, the corneal reflection can be determined; see, for example, " Mapping the Pupil-Glint Vector to Gaze Coordinates in a Simple Video-Based Eye Tracker / [Mapping the Pupil Glint Vector to Gaze Coordinates in a Simple Video-Based Eye Tracker]", Journal of Eye Movement Research 7(1):4, pp. 1-11, 1995 by P. Blignaut. However, in principle, other reflections can also be recorded, particularly by means of a so-called "dual Purkinje eyetracker". Since the corneal reflection does not move without head movement, but the pupil changes position during eye movement, the rotation of the corresponding eye can be deduced therefrom. Here, the "pupil" denotes the incident opening present in each eye through which radiation in the form of light can enter the interior of the eye. In the opposite direction, the pupil can be regarded as an exit opening through which the line of sight of the user from the eye to the surrounding environment can be defined.

[0039] The camera can preferably be included in the same mobile communication device as the visual display unit. In particular, this can be the rear camera of the mobile communication device, or preferably the front camera. In this way, a desired image sequence of the eye region of the user can be advantageously recorded by the camera at any desired position. However, other types of cameras can be envisioned, such as cameras that can be worn as a glasses-like device and are separated from the visual display unit. The disadvantage of this is that synchronization between the display and the camera is required.

[0040] Furthermore, a lighting device can be provided, in particular in order to be able to acquire the eye movement metrics of the user with the highest possible resolution and high contrast by means of a camera. As an alternative or in addition thereto, daylight or existing lighting can be used.

[0041] In a specific configuration, the camera can be sensitive in the infrared spectral range, i.e., at wavelengths from 780 nm to 1 mm, preferably from 780 nm to 3 µm, in particular at wavelengths from 780 nm to 1.4 µm (also referred to as "IR-A" according to Section 4.4 of the standard). To provide infrared radiation, a light source that emits light in the infrared spectral range can be provided for this purpose, in particular light of a wavelength to which the camera has sufficient sensitivity. The light source can preferably be selected from miniature incandescent lamps, solid-state-based IR emitters, light-emitting diodes, or infrared lasers, where appropriate filters can be used.

[0042] According to step c), a time point is preferably established while performing step b), which is defined by the following: at the established time point, it is evident from the observation of the eye movement metrics of the user that the user's recognition threshold for at least one symbol represented on the visual display unit. For this purpose, step b) can be repeated for different values of at least one parameter, preferably until the desired time point has been established by performing step c). In this case, the term "recognition threshold" represents the fact that the user can just still perceive or just perceive at least one symbol represented on the visual display unit as a stimulus for at least one eye. If at least one parameter of at least one symbol (in particular the spatial frequency in a periodic pattern) is gradually increased, the time point at which at least one symbol represented on the visual display unit can no longer act as a stimulus for at least one eye of the user can be established during this process. Conversely, if at least one parameter of at least one symbol (in particular the spatial frequency in a periodic pattern) is gradually decreased, the time point at which at least one symbol first represented on the visual display unit cannot act as a stimulus for at least one eye of the user can be established during this process. Alternatively, for example, if at least one parameter of at least one symbol (in particular the spatial frequency in a periodic pattern) is gradually decreased, the time point at which at least one symbol represented on the visual display unit can just act as a stimulus for at least one eye of the user can also be established during this process. Conversely, in this case, if at least one parameter of at least one symbol (in particular the spatial frequency in a periodic pattern) is gradually increased, the time point at which at least one symbol first represented on the visual display unit can act as a stimulus for at least one eye of the user can be established during this process.

[0043] In a particularly preferred configuration of the present invention, it can be seen from the user's reaction that the time point of the recognition threshold of at least one symbol represented on the visual display unit for the user can be established by virtue of the fact that the eye movement metric of the user just still follows or has just started to follow the movement of at least one symbol represented on the visual display unit. In particular, for this purpose, the eye tracking movement of the user can be used to establish the desired time point, by which the user follows the movement of at least one symbol that at least one eye of the user is gazing at. In particular, as described above, the eye tracking movement does not occur automatically, but follows the movement of at least one symbol represented on the visual display unit and serving as a stimulus for at least one eye of the user.

[0044] For this purpose, preferably, during step c), the evaluation unit can establish the desired time point of the user's recognition threshold (in particular the spatial frequency of at least one pattern) of at least one symbol represented on the visual display unit according to the eye movement metric of the user. For this purpose, the data for collecting the eye movement of the user recorded by the camera and transmitted to the evaluation unit can preferably be used to determine the line of sight of the user to at least one symbol represented on the visual display unit. In the case where at least one parameter of at least one symbol (in particular the spatial frequency of the periodic pattern) gradually decreases, as long as the user can recognize at least one symbol represented on the visual display unit, the eye tracking movement of the user will correspond to the movement of at least one symbol on the visual display unit. Once the time point is reached when the user can just no longer recognize at least one symbol (in particular the periodic pattern) represented on the visual display unit and thus the symbol can no longer act as a stimulus for at least one eye of the user, the eye tracking movement of the user will deviate from the movement of at least one symbol on the visual display unit. On the contrary, if the time point is reached when the user can just first recognize at least one symbol (in particular the periodic pattern) represented on the visual display unit and thus the symbol can first act as a stimulus for at least one eye of the user, the eye tracking movement of the user will now start to follow the movement of at least one symbol on the visual display unit. Regardless of the type of configuration, in this context, it is preferable to be able to set a threshold, by which the degree of deviation of the eye tracking movement of the user from the movement of at least one symbol on the visual display unit is established as the time point according to step c). In this case, the time point when the deviation exceeds or drops below the defined threshold represents the time point sought according to step c).

[0045] According to step d), the value of the refractive error of at least one eye of the user is determined based on the value of at least one parameter of at least one parameter used to set the selection of at least one symbol on the visual display unit at the established time, which is preferably carried out after the established time point and preferably in the evaluation unit. In the above preferred configuration, the value of the refractive error can be determined based on the spatial frequency of at least one pattern established at the time point, and this spatial frequency can also be the limiting frequency of the pattern. For this spatial frequency, it is evident from the observation of the eye movement metrics of the user during step c) what the recognition threshold of the user for at least one symbol represented on the visual display unit is. "Limiting frequency" means the spatial frequency of at least one pattern at which the contrast sensitivity becomes zero or the contrast of the stimulus becomes maximum. This frequency can also be considered as the resolution limit of the visual system.

[0046] In a particularly preferred configuration of the invention, first the contrast sensitivity of at least one eye of the user can be determined based on the parameters established at the time point. In this case, the term "contrast sensitivity of at least one eye" defines the measure for distinguishing different gray levels, as the reciprocal of the smallest, just still perceptible difference between two gray level values. The terms "visual acuity and visual discrimination of at least one eye of the user" respectively specify the measure of the spatial distance between two points that the at least one eye of the user can still perceive as distinguishable. In the above preferred configuration, the contrast sensitivity can be determined by a periodic pattern in the form of stripes arranged periodically adjacent to each other, and this pattern is also referred to as a "sinusoidal grating" or a "Gabor patch". In a preferred representation, a contrast sensitivity function can be defined for this purpose, where the contrast sensitivity is plotted against the spatial frequency of the periodic pattern. This function adopts different curves for the selected defocus of at least one eye of the user respectively. By determining which curve the contrast sensitivity of at least one eye of the user has, the current defocus of at least one eye and the spherocylindrical configuration of the spectacle lens can be determined, which produces a profound compensation for the refractive error of at least one eye and thus makes the image quality as optimal as possible for the user, and thereby the value of the refractive error of at least one eye of the user can be determined. For other details regarding the optical and neural components of the contrast sensitivity function, reference is made to " Individual neural transfer function affects the prediction of subjective depth of focus / [Individual neural transfer functions influence the prediction of subjective depth of focus]" (Scientific Reports 2018, 8(1), 1919), and for the corresponding determination of the value of the refractive error, reference is made to the exemplary embodiments.

[0047] Refractive error in at least one eye of a user causes defocus, and thus causes a reduction in a parameter that can still be optically resolved (e.g., at least one contrast of the spatial frequency of at least one represented pattern). If now the contrast sensitivity function of at least one eye is determined, this function is the product of an optical component (e.g., a physical modulation transfer function) and a neural component (e.g., a neural transfer function). The refractive error causes at least one change in at least one parameter (preferably the contrast of at least one spatial frequency, preferably the cut-off frequency), which can be mathematically modeled for the corresponding refractive error. This change that can be mathematically modeled for the corresponding refractive error causes a change in the contrast sensitivity function that can be mathematically modeled. Thus, the effect of the refractive error on the parameter that can still be optically resolved is determined. According to the invention, it is preferably assumed that the neural transfer function is a constant function, and the knowledge of the mathematical modeling of the contrast sensitivity function and the physical modulation transfer function of at least one eye is used to determine the possible refractive error present.

[0048] In the present invention, refractive error should be understood to mean the sub-optimal refraction of light in at least one eye, in which case the image plane of the eye for light rays from infinity does not lie at the intersection point of all light rays from infinity. In this case, as a spherical-cylindrical refractive error, the refractive error preferably includes a spherical aberration and a cylindrical aberration and their axes. The refractive error is determined for the following: for distance vision, preferably similar to DIN 58220-5:2013-09, section 5, table 1, the test distance between at least one symbol and the entrance pupil of the eye ≥ 4 m, with a maximum deviation of 3%; and / or for near vision, preferably the test distance between at least one symbol and the entrance pupil of the eye < 4 m, or more preferably similar to DIN 58220-5:2013-09, section 5, table 1, the test distance between at least one symbol and the entrance pupil of the eye is 0.400 m or 0.333 m or 0.250 m, with maximum deviations of 5% respectively. In addition, the refractive error for intermediate vision can also be determined, preferably similar to DIN58220-5:2013-09, the test distance between at least one symbol and the entrance pupil of the eye is 1.000 m or 0.667 m or 0.550 m, with maximum deviations of 5% respectively.

[0049] If the refractive error in at least one eye of a user has been corrected, for example, by at least one corrective lens (i.e., an ophthalmic lens with a refractive power according to section 8.1.3 of the standard), the method according to the invention for determining the refractive error in at least one eye can be used. If the refractive error in at least one eye is corrected, the method according to the invention can be used, for example, to check whether there is a change in the refractive error. If there is a change in the refractive error, the method according to the invention can be used to determine the change in the refractive error.

[0050] The method for determining the refractive error of at least one eye according to the present invention can also be used when the possible refractive error of at least one eye has not been corrected (e.g., by at least one corrective lens). By the method according to the present invention, it can also be established whether there is even a refractive error of at least one eye. In the case of a known refractive error, it is also possible to determine a change in the refractive error without, for this purpose, correcting the known refractive error, for example, by a corrective lens. When at least one eye of the user has not been corrected, the method for determining the refractive error of at least one eye according to the present invention is preferably applied.

[0051] In particular, by determining the refractive error of the user, it is thus possible to determine the spherocylindrical lens to be used as an eyeglass lens to compensate for the refractive error that occurs as defocus in at least one eye, so that the user can obtain the best possible image quality. Various expressions are suitable for describing the spherocylindrical lens. The standard defines in Section 11.2 the so-called "spherical power", which is defined as the value of the back vertex power of an eyeglass lens with spherical power or the corresponding back vertex power on one of the two principal meridians of an eyeglass lens with astigmatism. According to Sections 9.7.1 and 9.7.2 of the standard, the "vertex power" is defined as the reciprocal of the paraxial back focal length of the back focal point measured in meters, respectively. According to Section 12 of the standard, a spherocylindrical eyeglass lens with astigmatism combines a paraxial parallel beam of light into two separate focal lines perpendicular to each other and thus has only spherical vertex power on the two principal meridians. According to this standard, the "astigmatism" is defined by the cylinder power and the axis position. In this case, the "cylinder strength" according to Section 12.5 of this standard represents the absolute value of the "astigmatic difference", which indicates the difference between the vertex powers on the two principal meridians. According to Section 12.6 of this standard, the "axis position" represents the direction of the principal meridian for which the vertex power is used as a reference value. Finally, according to Section 12.8 of the standard, the "strength" of an eyeglass lens with astigmatism is specified by three values, including the vertex power of each of the two principal meridians and the cylinder strength.

[0052] According to L. N. Thibos, W. Wheeler, and D. Horner (1997), " Power Vectors:An Application of Fourier Analysis to the Description and Statistical Analysis of Refractive Error / [The Refractive Error Vector: Application of Fourier Analysis to the Description and Statistical Analysis of Refractive Error]", Optometry and Vision Science 74 (6), pp. 367 - 375, in order to describe any spherocylindrical lens and / or refractive error, which are respectively suitable for specifying the "refractive error vector" that can be described by exactly one point in a three-dimensional refractive space, where the three-dimensional refractive space can be spanned by coordinates corresponding to or related to the mean spherical refractive power and the cylinder strength.

[0053] In a specific configuration, at least one symbol, in particular at least one periodic pattern, can first be represented in a first direction and subsequently in a second direction, which second direction can be arranged perpendicular to the first direction. In this way, the vertex power values of each of the two mutually perpendicular principal meridians of a spherocylindrical spectacle lens with astigmatism can be determined successively.

[0054] Thus, it is possible to particularly advantageously dispense with a psychophysical algorithm for determining the refractive error of at least one eye. In this context, the term "psychophysical algorithm" denotes a process based on the regular interaction between the subjective mental, psychological experiences of the user and the objectively physically measurable, quantitative stimuli that trigger the user's experience. Instead, according to the invention, measurement variables in the form of eye movement metrics are used, and conclusions about the user's response can be drawn from these measurement variables based on at least one stationary or moving symbol (such as a spatial frequency that varies over time).

[0055] In a further configuration, the individual steps of the method for determining the refractive error of at least one eye of a user are carried out by means of at least one mobile communication device. Preferably, the at least one mobile communication device is to be understood as referring to a device which comprises at least one programmable processor and at least one camera as well as at least one acceleration sensor and which is preferably designed to be carried, i.e. configured in terms of size and weight such that a person can carry it. Other components may be present in the at least one mobile communication device, such as at least one visual display unit, at least one light source for visible light in the wavelength range from, for example, 380 nm to 780 nm and / or infrared light in the wavelength range from 780 nm to 1 mm and / or at least one light receiver sensitive to visible light in the wavelength range from, for example, 380 nm to 780 nm and / or infrared light in the wavelength range > 780 nm to 1 mm. As described above, a typical example of such a mobile communication device is a smartphone or a tablet PC, which may comprise at least one visual display unit, such as a sensor visual display unit (touch screen), at least one camera, at least one accelerometer, at least one light source, at least one light receiver, and other components, such as a wireless interface for mobile radio and WLAN (wireless LAN). According to step a) of the method according to the invention, representing at least one symbol can be carried out, for example, by means of at least one visual display unit of at least one mobile communication device. According to step b) of the method according to the invention, acquiring the eye movement metrics of at least one eye can be carried out, for example, by means of at least one camera of at least one mobile communication device or by means of at least one light source and at least one camera of at least one mobile communication device. According to step c) of the method according to the invention, establishing the time point at which the recognition threshold of at least one symbol represented on the visual display unit by the user becomes apparent from the eye movement metrics of at least one user can be carried out, for example, by means of at least one camera of at least one mobile terminal or by means of at least one light source and at least one camera of at least one mobile terminal. In addition, at least one camera of the mobile communication device may comprise at least one autofocus system. The at least one camera may have a zoom objective with variable viewing angle or an objective with at least two different viewing angles. If the at least one camera has at least one distance sensor, the distance between the visual display unit of the mobile communication device and the user's eye can be determined, for example, by means of a signal from the distance sensor. If the camera has at least two objectives, these two objectives may have the same viewing angle or different viewing angles and may be spatially separated from each other in the lateral direction, and the distance between the camera of the mobile communication device and the user's eye can be determined, for example, by means of a triangulation method. In the latter case, the viewing angles of the at least two objectives are preferably the same.

[0056] In a further aspect, the present invention relates to a computer program for determining the refractive error of at least one eye of a user, wherein the computer program is arranged to determine the refractive error of at least one eye of the user according to the method for determining the refractive error of at least one eye of a user described herein.

[0057] In a further aspect, the present invention relates to a method for manufacturing spectacle lenses, wherein the spectacle lenses are manufactured by processing a lens blank (Standard Section 8.4.1) or a spectacle lens semi-finished product (Standard Section 8.4.2), wherein the lens blank or the spectacle lens semi-finished product is processed respectively based on refractive data and optionally centering data, wherein the refractive data and optionally the centering data include instructions for compensating the refractive error of at least one eye of the user, and wherein the determination of the refractive error of at least one eye of the user is carried out according to the method for determining the refractive error of at least one eye of a user described herein. The refractive data preferably includes corrections for the refractive error of at least one eye of the user for distance vision and / or near vision with respect to spherical correction and astigmatic correction of the axis position. The centering data preferably includes at least

[0058] - according to Standard Section 17.3, the face curve of the spectacle frame, the angle between the spectacle frame plane and the right or left lens plane, and / or

[0059] - the coordinates of the centering point, i.e., the absolute value of the distance between the centering point and the nasal vertical edge or the horizontal lower edge of the box system, measured in the lens plane according to Standard Section 17.4, and / or

[0060] - the corneal vertex distance, i.e., the distance between the posterior surface of the spectacle lens and the corneal vertex measured in the viewing direction perpendicular to the spectacle frame plane according to Standard Section 5.27, and / or

[0061] - the "wearing" rake angle or rake angle, i.e., according to Standard Section 5.18, the angle in the vertical plane between the normal to the center of the front surface of the spectacle lens according to the box system and the line of sight of the eye in the primary position of gaze (usually assumed to be horizontal), and / or

[0062] - an optional distance vision point, i.e., according to Standard Section 5.16, the assumed position of the viewing point for distance vision on the spectacle lens under given conditions, and / or

[0063] - an optional near vision point, i.e., according to Standard Section 5.17, the assumed position of the viewing point for near vision on the spectacle lens under given conditions.

[0064] In another aspect, the present invention relates to a device for determining the refractive error of at least one eye of a user. According to the present invention, the device comprises

[0065] - A visual display unit configured to represent at least one symbol and at least one change in at least one parameter of the at least one symbol;

[0066] - A camera, preferably a video camera, configured to acquire an eye movement metric of at least one eye of a user based on at least one symbol represented on the visual display unit; and

[0067] - An evaluation unit configured to: establish a time point at which a recognition threshold of at least one symbol represented on the visual display unit by the user is evident from the eye movement metric of at least one eye of the user, and determine a value of the refractive error of at least one eye of the user based on the parameter defined at that time point.

[0068] In a particularly preferred configuration, the evaluation unit may also have means for acquiring the distance between at least one eye of the user and the visual display unit or the camera, such as a video camera. For this purpose, by performing image processing on a sequence of images of the eye region of the user recorded in particular by the camera (such as a video camera), especially when the calibration of the pixels of the camera exists in spatial units, the pupil diameter of at least one eye of the user is determined from the determination of the pupil distance between the camera (such as a video camera) and at least one eye of the user. In a preferred configuration, at least two cameras may be provided, which are arranged together in the form of a stereo camera and are thus configured to acquire the distance between at least one eye of the user and the visual display unit. Alternatively or additionally, the device may include a distance measurement unit configured to determine the pupil distance between the camera (such as a video camera) and at least one eye of the user.

[0069] Reference is made to the above or below description of the method for determining the refractive error of at least one eye of a user for the definition and optional configuration of a computer program and a device for determining the refractive error of at least one eye of a user, as well as for the definition and optional configuration of a method for manufacturing spectacle lenses, including the features cited therein.

[0070] When selecting at least one new spectacle lens for a user, the device and the existing method according to the invention can be particularly used. As an alternative or in addition thereto, however, it can also be used when checking at least one existing spectacle lens of the user. In the latter case, when performing the method for determining the refractive error, the user can wear glasses, and a deviation from the optimal refraction can be established through an optical system including the eye and at least one spectacle lens of the user. The value of at least one spectacle lens determined in this process can additionally be used for selecting and manufacturing additional glasses, which can be used, for example, as spectacle replicas or spare glasses.

[0071] The device and the method according to the invention have a number of advantages over conventional devices and methods. This can be used to objectively determine the correction of the refractive error of at least one eye of a user without the need for professional equipment, in particular without subjective feedback from the user, such as subjective feedback in the form of manual or acoustic input into the device. The proposed device is not limited to one location and can in particular also be used by non-professionals during the process. Furthermore, the contrast sensitivity determined by collecting eye movement metrics is advantageously used to determine the correction, in order to thus easily determine the refractive error of at least one eye of the user.

[0072] In summary, in the context of the present invention, the following embodiments are particularly preferred:

[0073] Embodiment 1. A method for determining the refractive error of at least one eye of a user, wherein the method comprises the following steps:

[0074] a) Representing at least one symbol on a visual display unit, wherein at least one parameter of the at least one symbol represented on the visual display unit is variable;

[0075] b) Collecting eye movement metrics of at least one eye of the user based on the at least one symbol represented on the visual display unit;

[0076] c) Establishing a time point at which the recognition threshold of the user for the at least one symbol represented on the visual display unit is apparent from the eye movement metrics of at least one eye of the user; and

[0077] d) Determining the value of the refractive error of at least one eye of the user according to the parameter defined at this time point.

[0078] Embodiment 2. The method according to the previous embodiment, wherein the refractive error of one eye or both eyes of the user is determined.

[0079] Embodiment 3. The method according to any one of the preceding embodiments, wherein at least one parameter of the at least one symbol represented on the visual display unit is variable while the at least one symbol represented on the visual display unit moves on the visual display unit.

[0080] Embodiment 4. The method according to the previous embodiment, wherein the movement of the at least one symbol represented on the visual display unit is carried out continuously or in jumps.

[0081] Embodiment 5. The method according to any one of the previous two embodiments, wherein the time point is established by means of eye movement metrics in which the user just still follows or just follows the movement of the at least one symbol represented on the visual display unit.

[0082] Example 6. The method according to any one of the preceding examples, wherein step b) is repeated for different values of at least one parameter.

[0083] Example 7. The method according to the previous example, wherein step b) is repeated for different values of at least one parameter until the time point according to step c) is established.

[0084] Example 8. The method according to any one of the preceding examples, wherein the eye movement metric involves: eye pursuit movement; eye movement associated with microsaccades; or optokinetic nystagmus.

[0085] Example 9. The method according to the previous example, wherein the eye movement associated with microsaccades is selected from: microsaccade direction or microsaccade rate.

[0086] Example 10. The method according to the previous example, wherein the eye movement metric associated with microsaccades is used as a metric for establishing whether the user has recognized a symbol as a stimulus.

[0087] Example 11. The method according to the previous example, wherein the eye movement metric associated with saccades is selected from the accuracy of the executed saccades relative to the spatial position of the stimulus on the visual display unit, and this eye movement metric is used as a metric for determining whether the user has recognized at least one symbol as a stimulus.

[0088] Example 12. The method according to the previous example, wherein the eye movement metric associated with optokinetic nystagmus is selected from: the phase correspondence between the eye pursuit movement and the movement of the stimulus on the visual display unit, which is used as a metric for determining whether the user has recognized at least one symbol as a stimulus.

[0089] Example 13. The method according to any one of the preceding examples, wherein the contrast sensitivity value of at least one eye of the user is first determined according to at least one parameter established at this time point.

[0090] Example 14. The method according to the previous example, wherein a contrast sensitivity function is established, and this contrast sensitivity function is fitted to the determined value of the contrast sensitivity of at least one eye of the user.

[0091] Example 15. The method according to the previous example, wherein the defocus of at least one eye of the user is determined according to the established contrast sensitivity function.

[0092] Example 16. The method according to the previous example, wherein the refractive error value of at least one eye of the user is determined according to the defocus of at least one eye of the user.

[0093] Example 17. The method according to any one of the four foregoing embodiments, wherein the refractive error value of at least one eye of the user is determined based on the contrast sensitivity of at least one eye of the user.

[0094] Example 18. The method according to any one of the foregoing embodiments, wherein at least one symbol is or includes a periodic pattern.

[0095] Example 19. The method according to the previous embodiment, wherein at least one parameter of at least one pattern represented on the visual display unit is or includes at least one spatial frequency.

[0096] Example 20. The method according to any one of the foregoing embodiments, wherein the at least one symbol is first represented in a first direction with respect to the orientation of the visual display unit and subsequently represented in a second direction that has changed with respect to the first direction.

[0097] Example 21. The method according to the previous embodiment, wherein the vertex power of one of two principal meridians perpendicular to each other of a spherocylindrical spectacle lens having astigmatism is determined successively.

[0098] Example 22. The method according to any one of the foregoing embodiments, wherein the distance between at least one eye of the user and the visual display unit is additionally acquired.

[0099] Example 23. The method according to the previous embodiment, wherein the distance between at least one eye of the user and the visual display unit is the pupil distance.

[0100] Example 24. The method according to any one of the two foregoing embodiments, wherein the distance is acquired by a distance measuring unit.

[0101] Example 25. The method according to any one of the three foregoing embodiments, wherein the distance is acquired by a camera such as a video camera.

[0102] Example 26. The method according to any one of the four foregoing embodiments, wherein the distance is acquired by at least two cameras that are jointly configured to acquire the distance.

[0103] Example 27. The method according to the previous embodiment, wherein the at least two cameras are jointly arranged in the form of a stereo camera.

[0104] Example 28. The method according to any one of the foregoing embodiments, wherein the method is performed when the user is wearing glasses.

[0105] Example 29. A computer program for determining the refractive error of at least one eye of a user, wherein the computer program is configured to perform the steps according to any one of the foregoing examples.

[0106] Example 30. A method for manufacturing at least one spectacle lens, wherein the spectacle lens is manufactured by machining a lens blank or a semi-finished spectacle lens, wherein the lens blank or the semi-finished spectacle lens is machined based on refractive data and optionally centering data respectively, wherein the refractive data and optionally the centering data include instructions for compensating the refractive error of at least one eye of a user, and wherein the determination of the refractive error of at least one eye of a user is carried out according to the steps according to any one of the foregoing examples related to the method for determining the refractive error of at least one eye of a user.

[0107] Example 31. An apparatus for determining the refractive error of at least one eye of a user, wherein the apparatus comprises:

[0108] - a visual display unit configured to represent at least one symbol and a change in at least one parameter of the at least one symbol;

[0109] - a camera, such as a video camera, configured to acquire an eye movement measure of at least one eye of the user based on at least one symbol represented on the visual display unit; and

[0110] - an evaluation unit configured to: establish a time point at which a recognition threshold of the user for at least one symbol represented on the visual display unit is apparent from the eye movement measure of at least one eye of the user, and determine a value of the refractive error of at least one eye of the user according to at least one parameter defined at the time point.

[0111] Example 32. The apparatus according to the previous example, wherein the apparatus further comprises a distance measurement unit, and wherein the distance measurement unit is further configured to determine the distance between the apparatus and at least one eye of the user.

[0112] Example 33. The apparatus according to any one of the two previous examples, wherein the camera, such as a video camera, is configured to record an image of at least one eye of the user, and wherein the evaluation unit is further configured to determine the distance between the apparatus and at least one eye of the user by performing image processing on the image of at least one eye of the user.

[0113] Example 34. The apparatus according to any one of the three previous examples, wherein at least two cameras are provided, and the at least two cameras are jointly configured to acquire the distance between the apparatus and at least one eye of the user.

[0114] Example 35. The device according to the previous example, wherein the at least two cameras are arranged together in the form of a stereo camera.

[0115] Example 36. The device according to any one of the previous five examples, wherein the device is configured as a mobile communication device, which includes a visual display unit, a camera, an evaluation unit and optionally a distance measurement unit.

[0116] Example 37. The device according to the previous example, wherein the mobile communication device is configured as a smartphone.

[0117] On the other hand, the above method and / or the above device and / or the above computer program can be used together with at least one additional method and / or at least one additional device and / or an additional computer program. The at least one additional method can be, for example, a method for determining the refractive error of a user's eye, preferably according to the method of EP 19170558.1, wherein the method includes the following steps:

[0118] a) Representing characters on the visual display unit, wherein the parameters of the characters represented on the visual display unit are variable;

[0119] b) Acquiring the user's reaction depending on the characters represented on the visual display unit;

[0120] c) Establishing the time point at which it is evident from the user's reaction that the user can recognize the characters represented on the visual display unit; and

[0121] d) Determining the value of the refractive error of the user's eye according to the parameters defined at this time point, wherein the characters represented on the visual display unit are periodic patterns, wherein the parameters of the patterns represented on the visual display unit include at least one spatial frequency, and the refractive error is determined according to the spatial frequency of the pattern defined at this time point.

[0122] As an alternative to or in addition to the above method, at least one additional method can also be, for example, a method for determining at least one optical parameter of spectacle lenses, preferably according to the method of EP 19170551.6, wherein this method includes the following steps:

[0123] a) Recording an image using the spectacle lenses; and

[0124] b) Determining at least one optical parameter of the spectacle lenses by image processing of the image, wherein the image includes an eye region, which includes the user's eye of the spectacle lenses and / or the facial region adjacent to the eye.

[0125] As an alternative to or in addition to the above method, at least one further method can also be, for example, a method for measuring the refractive power distribution of the left and / or right spectacle lenses in a spectacle frame, preferably the method according to EP 19170715.7, in which, in a first step, at least one image acquisition device is used to acquire at least one first imaging of a scene from at least one first recording position, wherein the at least one first imaging has at least two structural points and includes the left and / or right spectacle lenses in the spectacle frame, a section of the spectacle frame defining the coordinate system of the spectacle frame, and at least one imaging beam path of each of the at least two structural points passing through and at least once not passing through the first and / or second spectacle lenses of the spectacle frame respectively. Each imaging beam path includes the position of the structural point and also the chief ray incident on the at least one image acquisition device. A further step, which can be before or after the first step in time, includes acquiring at least one further imaging of the scene without the first and / or second spectacle lenses of the spectacle frame or without the spectacle frame including the first and / or second spectacle lenses, wherein the same at least two structural points of the first imaging of the scene by the at least one image acquisition device are from the first recording position or from at least one further recording position different from the first recording position. The at least one image acquisition device in the further step can be the same as or different from the at least one image acquisition device in the first step. Preferably, the at least one image acquisition device in the further step is the same as the at least one image acquisition device in the first step. Then, in a calculation step, the coordinates of the at least two structural points are determined by image evaluation of the image representation of the scene generated by the at least one beam path of the at least two structural points (which beam path does not pass through the left and / or right spectacle lenses respectively) in a coordinate system that references the coordinate system of the spectacle frame and the at least one further image representation of the scene. After this step, in the step of determining the refractive power distribution of at least one section of the left spectacle lens in the coordinate system of the spectacle frame and / or in the step of determining the refractive power distribution of at least one section of the right spectacle lens in the coordinate system of the spectacle frame, the refractive power distribution is determined respectively from the imaging beam paths that have passed through the respective spectacle lenses.

[0126] As an alternative to or in addition to the above method, at least one further method can for example also be a method for measuring the refractive power distribution of the left and / or right spectacle lenses in a spectacle frame, preferably the method according to EP 19170715.7, in which, in a first step, at least one image acquisition device is used to acquire at least one first imaging of the scene from at least one first recording position, wherein the at least one first imaging has at least two structural points and includes the left and / or right spectacle lenses in the spectacle frame, a section of the spectacle frame defining the coordinate system of the spectacle frame, wherein at least one imaging beam path of each of these at least two structural points passes through and at least once does not pass through the first and / or second spectacle lenses of the spectacle frame at least once. Each imaging beam path includes the position of the structural point and also the chief ray incident on the at least one image acquisition device. Further steps that can be carried out before or after or simultaneously with the first step in time include using the left and / or right spectacle lenses in the spectacle frame and the section of the spectacle frame defining the coordinate system of the spectacle frame to acquire at least one further imaging of the scene from at least one further recording position different from the first recording position by means of at least one image acquisition device, at least one imaging beam path for the same at least two structural points acquired in the first imaging, wherein the at least one imaging beam path passes through and at least once does not pass through the first and / or second spectacle lenses of the spectacle frame at least once. This is followed by a further step which includes calculating, by image evaluation, the coordinates of the at least two structural points in the coordinate system (referencing the coordinate system of the spectacle frame) of the scene of the at least one beam path that has accordingly not passed through the left and / or right spectacle lenses and of the at least one further imaging of the scene. Subsequently, from these imaging beam paths that have passed through the respective spectacle lenses, the refractive power distribution of at least one section of the left lens in the coordinate system of the spectacle frame and / or the refractive power distribution of at least one section of the right lens in the coordinate system of the spectacle frame is determined.

[0127] Preferably, in the above two methods for measuring the refractive power distribution of the left and / or right spectacle lenses, preferably in the spectacle frame, a plurality of structural points are acquired in the respective first imaging of the scene from respectively at least one first recording position, and the respective subsequent steps are carried out based on this respective plurality of structural points. The plurality of structural points should be understood to mean preferably at least 10, more preferably at least 100, particularly preferably at least 1000, very particularly preferably at least 10000 structural points. In particular, the plurality of structural points ≥ 100 structural points and ≤ 1000 structural points.

[0128] As an alternative to or in addition to the above method, at least one further method can also be, for example, a method for determining the refractive power distribution of an ophthalmic lens, preferably according to the method of EP 19170714.0, such that, for example, it becomes possible to derive the local refractive power from a comparison of the size and / or shape of the imaging of the anterior eye segment from a specific viewing direction. This is done by performing at least one recording of the anterior eye segment when the ophthalmic lens is in front of the anterior eye segment and when the ophthalmic lens is not in front of the anterior eye segment, and accordingly comparing the recordings with and without the ophthalmic lens with each other.

[0129] In a higher-level application, the various methods described above, namely the method according to the invention and also at least one further method, can be combined in sequence from a comparison of the results obtained separately, for example, to obtain a higher accuracy or to perform a plausibility check on the results obtained in the individual methods. The various methods can be implemented successively or simultaneously in the higher-level application. If the various methods are implemented successively, their order can be independent of each other and / or can relate to any desired order. If the various methods are implemented successively, it is preferably at least one method of the above methods for determining the refractive power distribution that is performed last. The higher-level application can be, for example, a computer program that includes the various methods. Description of the Drawings

[0130] Further details and features of the invention will become apparent from the following description of preferred exemplary embodiments, in particular in conjunction with the dependent claims. In this case, the corresponding features can be implemented only by themselves or in combinations with each other as a plurality. The invention is not limited to these exemplary embodiments. The exemplary embodiments are schematically illustrated in the drawings. In this case, the same reference numerals in the various figures denote identical or functionally identical elements or elements that correspond to each other in terms of their function. Specifically:

[0131] Figure 1 shows a preferred exemplary embodiment of a device for determining the refractive error of a user's eye;

[0132] Figure 2 shows a schematic representation in which the contrast sensitivity of a user's eye ε is plotted against the spatial frequency of a periodic pattern f and;

[0133] Figure 3 shows a flow chart of a preferred exemplary embodiment of a method for manufacturing at least one ophthalmic lens according to the invention. Detailed Description

[0134] Figure 1A preferred exemplary embodiment of a device 110 for determining the refractive error of an eye 112 of a user 114 is schematically shown. In this case, the device 110 can be used to determine the refractive error of one or both eyes 112 of the user 114. In accordance with Figure 1 the illustration and the following description, without loss of generality, the proposed device 110 is implemented as a mobile communication device 116 in the form of a smart phone 118. However, embodiments of the device 110 in the form of some other mobile communication device 116, in particular a cellular phone (mobile phone) or a tablet computer, are equally conceivable.

[0135] The device 110 includes a visual display unit 120, which is substantially in the rectangular shape as shown in Figure 1 . However, other shapes of the visual display unit 120 are also possible. The visual display unit 120 is configured to represent a symbol 122. In a preferred embodiment of the present invention, the symbol 122 represents a pattern 124, which includes a graphic structure - in particular, compared with noise having no recognizable structure, a graphic structure having at least one spatially oriented period within which the structure of the pattern 124 is repeatedly represented. Therefore, this pattern is also referred to as a periodic pattern.

[0136] In addition, the visual display unit 120 is configured to represent a change in the parameters of the symbol 122 represented on the visual display unit. Due to the electronic control of the visual display unit 120 on the smart phone 118, the selected parameters of the pattern 124 represented on the visual display unit can be easily varied within a wide range. In the periodic pattern 124 presented here, the parameters can preferably be associated with the characteristics of a periodic function. In particular, in this case, a repetition frequency can be used, at which the structure can be repeatedly presented in such a way that due to this repetition, similar points or regions can be formed on the structure of the pattern 124. In accordance with Figure 1 the illustration, the periodic maxima 126 and minima 128 can be recognized as a preferred configuration of similar points or regions of the pattern 124. The periodic function used here is a sine function. However, other periodic functions are conceivable, such as a cosine function or a superposition of a cosine function and a sine function.

[0137] In accordance with Figure 1 the parameters of the symbol represented on the visual display unit 120, at least one spatial frequency of the periodic pattern 124, where the term "spatial frequency" represents the reciprocal of the spatial distance 130 between adjacent similar points (in particular, the spatial distance between adjacent maxima 126 or adjacent minima 128) in the spatial periodic variation of the pattern 124. However, other ways of determining the spatial frequency according to the pattern 124 are conceivable, such as according to the spacing of points of equal intensity.

[0138] As Figure 1 Further shown, in this particularly preferred embodiment, the periodic pattern comprises a two-dimensional superposition of periodic functions, in particular a sine function (which extends in a first direction 132 along the extent of the visual display unit 120) and a constant function (which extends in a second direction 134 along the extent of the visual display unit 120), where in this case the second direction is arranged perpendicular to the first direction 132. However, other angles between the first direction 132 and the second direction 134 are equally possible. In this way, the pattern 124 on the visual display unit 120 can exist in the form of stripes 136 arranged adjacent to each other in a periodic manner, which are also referred to as "sinusoidal gratings" or "Gabor patches". However, other types of patterns 124 are equally possible. Thus, the user 114 observes the sinusoidal grating on the visual display unit from a defined distance, which sinusoidal grating comprises stripes 136 having a high contrast and a plurality of spatial frequencies arranged adjacent to each other periodically. The distance can preferably be selected to have a value between 25 cm and 1 m, particularly a value between 40 cm and 75 cm, particularly a value of 50 cm.

[0139] In Figure 1 the particularly preferred embodiment of the invention illustrated, the spatial frequency of the pattern 124 represented on the visual display unit 120 varies, particularly when the pattern 122 represented on the visual display unit 120 performs a movement 138 on the visual display unit 120. In this case, the movement 138 of the pattern 124 represented on the visual display unit 120 can be continuous. Alternatively, the movement 138 of the pattern 124 can also be implemented in the form of jumps over the extent of the visual display unit 120. The change in the spatial frequency of the pattern 124 represented on the visual display unit 120 can in particular be implemented by initially representing a high spatial frequency and then gradually decreasing the high spatial frequency, or by initially representing a low spatial frequency and then gradually increasing the low spatial frequency. According to the invention, the value of the spatial frequency is set independently of the user 114.

[0140] The device 110 further comprises a camera 140, which is configured to acquire eye movement metrics 144 of the user 114 based on the pattern 124 represented on the visual display unit 120. As Figure 1Schematically illustrated in the figure, the camera 140 may preferably be the front camera 142 of the smart phone 118. However, other embodiments are possible. An image of the eye region 146 of the user 114 may be recorded by the camera 140, particularly when the user 114 observes the sine grating on the visual display unit 120 of the smart phone 118. If one of the parameters of the symbol 122 changes, particularly the spatial frequency in the periodic pattern 124, then the time point at which the symbol 122 represented on the visual display unit 120 can no longer serve as a stimulus for the eyes 112 of the user 114 can be established during this process. Conversely, if one of the parameters of the symbol 122 changes, particularly the spatial frequency in the periodic pattern 124, then the time point at which the symbol 122 represented on the visual display unit can first serve as a stimulus for the eyes 112 of the user 114 can be established during this process.

[0141] In Figure 1 In the particularly preferred configuration illustrated, the time point at which the recognition threshold of the symbol 122 represented on the visual display unit 120 is present can be seen clearly from the eye movement metric 144 of the user 114. This time point should be understood to mean that the user 114 can just still perceive or just barely perceive the symbol 122 represented on the visual display unit 120, and can be established by means of the eye movement metric 144 in which the user 114 just still follows or just begins to follow the movement 138 of the symbol 122 represented on the visual display unit 120. As described above, the eye movement metric 144 represents a metric associated with the movement of the eyes 112 of the user 114, where the movement of the eyes 112 of the user 112 is caused by the movement 138 and the change in the pattern 124 represented on the visual display unit 120 as an external stimulus acting on the eyes 112 of the user 114. The eye movement metric 144 recorded by the camera 140 can particularly be a change in eye pursuit movement, saccade direction, saccade rate, saccade accuracy, or optokinetic nystagmus, which occurs due to the change in the stimulus.

[0142] As Figure 1 Further schematically illustrated in the figure, the device 110 may additionally have a housing 148, which may include an evaluation unit 150. However, as an alternative or in addition to this, the evaluation unit 150 may also be attached outside the housing 148, where a wired or wireless connection (not illustrated) may be provided between the camera 140 and the evaluation unit 150. However, other types of implementations are also possible.

[0143] According to the present invention, the evaluation unit 150 is configured to establish a time point at which the recognition threshold of the user 114 for the symbol 122 represented on the visual display unit 120 is apparent from the eye movement metric 144 of the user 114, in particular the time point at which the user 114 just still recognizes or just recognizes the parameter (in particular the spatial frequency of the periodic pattern 124) of the symbol 122 represented on the visual display unit 120. For this purpose, the spatial frequency in the periodic pattern 124 can be increased or decreased in particular in the first direction 132, preferably during the movement 138 of the pattern, in time and / or space. At the same time, the camera 140 is used to determine the eye movement metric 144 of the user 114.

[0144] In a preferred embodiment, the data for acquiring the eye movement metric 144 of the user 114, which is recorded by the camera 140 and transmitted to the evaluation unit 150, can preferably be used for this purpose to determine the relevant eye movement metric 144 of the user 114 with respect to the symbol 122 represented on the visual display unit 120. In the case where one of the parameters of the symbol 122 recognizable by the user 114 changes, in particular where the spatial frequency in the periodic pattern 124 changes, as long as the user 114 can recognize the symbol 122 represented on the visual display unit 120, the eye tracking movement of the user 114 will correspond to the movement 138 of the symbol 122 on the visual display unit 120. If the time point is reached at which the user 144 can no longer recognize the symbol 122 (in particular the periodic pattern 124) represented on the visual display unit 120 and the symbol can therefore no longer act as a stimulus for the eye 112 of the user 114, the eye tracking movement of the user 114 will deviate from the movement 138 of the symbol 122 on the visual display unit 120. Conversely, if the time point is reached at which the user 114 can just recognize for the first time the symbol 122 (in particular the periodic pattern 124) represented on the visual display unit 120 and the symbol can therefore act as a stimulus for the eye 112 of the user 114 for the first time, the eye tracking movement of the user 114 will now start to follow the movement 138 of the symbol 122 on the visual display unit 120.

[0145] In a preferred embodiment, the evaluation unit 150 can preferably define a threshold in this process, through which the degree of deviation of the eye tracking movement of the user 114 from the movement 138 of the symbol 122 on the visual display unit 120 is established as the desired time point. However, other ways of establishing the desired time point are conceivable.

[0146] Thus, the desired image of the eye region 146 of the user 114 can be recorded by the camera 140 at any desired position. Geometric data of the pupil 152, in particular the relative position 154 and diameter 156 of the pupil 152 in the eye 112 of the user 114, can be determined from the recorded image sequence, in particular by image processing preferably performed by the evaluation unit 150. As an alternative or in addition thereto, the so-called "white-to-white distance" in the eye 112 of the user 114 can also be determined, for which standardized data is available.

[0147] According to the invention, the evaluation unit 150 is further configured to determine the value of the refractive error of the eye 112 of the user 114 based on an indication of the time point of the recognition threshold of the user 114 for the symbol 122 represented on the visual display unit 120 as apparent from the eye movement metric 144 of the user 114. For this purpose, the acquired data regarding the eye pursuit movement of the user 114 recorded by the camera 140 is transmitted to the evaluation unit 150, which is configured to determine the desired time point based on this data. In addition, due to the electronic control of the visual display unit 120 on the smart phone 118, the parameters of the symbol 122 represented on the visual display unit 120, in particular the spatial frequency of the periodic pattern 124, are known and can therefore be used by the evaluation unit 150 for the desired evaluation. For this purpose, in a particularly preferred embodiment, the evaluation unit 150 can also be configured to set the desired parameters of the symbol 122, in particular the spatial frequency of the periodic pattern 124, by controlling the visual display unit 120.

[0148] In a further embodiment, the distance between the camera 140 and the eye 112 of the user 114 (referred to as the pupil distance 158) can additionally be determined. A distance measurement can be performed to determine the pupil distance 158, preferably a distance measurement value already available in the smart phone 118. As an alternative or in addition thereto, when the camera 140 detects a known object or image content, the pupil distance 158 can be determined by triangulation via the known number of pixels of the camera 140. In particular, the pupil distance 158 can be used to be able to more accurately determine the distance in the symbol 122, in particular the aforementioned spatial distance 130 between adjacent similar points, in particular the spatial distance between adjacent maxima 126 or adjacent minima 128, which corresponds to the reciprocal of the spatial frequency in the periodic pattern 124.

[0149] In a particularly preferred embodiment of the invention, the contrast sensitivity of the eye 112 of the user 114 can first be determined based on the parameters of the symbol 122 (in particular the spatial frequency of the periodic pattern 124) established at the time point. ε . As described above, in this case, the contrast sensitivity εSpecifies a measure of the distance at which the eyes 112 of the user 114 can still be perceived as distinguishable, in particular the aforementioned spatial distance 130 between adjacent similar points, in particular the spatial distance between adjacent maxima 126 or adjacent minima 128, which distance corresponds to the reciprocal of the spatial frequency in the periodic pattern 124.

[0150] Figure 2 Shows a schematic diagram in which the contrast sensitivity of the eyes 110 of the user 114 determined according to the present method ε is plotted against the spatial frequency of the periodic pattern 124 f As Figure 2 schematically indicated by the symbol "x" of the corresponding measured values in, in this case, for different spatial frequencies f the contrast sensitivity of the eyes 112 of the user 114 can be determined ε According to the invention, it is proposed to fit the selected contrast sensitivity functions 160, 160', 160'' to the corresponding measured values to the best possible extent.

[0151] The curves of the contrast sensitivity functions 160, 160', 160" are known and have a bell-shaped curve, which typically reaches a maximum at a spatial frequency of 5 to 6 cycles / degree. The contrast sensitivity functions 160, 160', 160'' drop sharply towards higher spatial frequencies f while in embodiments where a drop towards lower spatial frequencies f is also observable it is less sharp. The corresponding maxima 162, 162', 162'' of the contrast sensitivity functions 160, 160', 160'' represent the maximum possible visual discrimination of the eyes 112 of the user 116. In addition, the areas 164, 164', 164'' below the contrast sensitivity functions 160, 160', 160'' can be considered as visible areas, meaning that the user 114 can only recognize those objects having a contrast and a structure located within the corresponding areas 164, 164', 164''.

[0152] From Figure 2It can be clearly seen that each of the contrast sensitivity functions 160, 160', 160'' represented here has a respective different curve, where each of the contrast sensitivity functions 160, 160', 160'' includes a selected defocus of the eye 112 as a parameter. Thus, exactly one of the contrast sensitivity functions 160, 160', 160'' can fit the acquired measurement value "x" to the best possible extent, since the eye 112 has exactly one defocus value. Accordingly, the associated defocus of the user 114's eye 112 can be determined based on the parameter of the contrast sensitivity function 160' with the best fit. Based on the defocus of the user 114's eye 112 thus determined, a spherocylindrical configuration of the spectacle lenses can be established, which produces a profound compensation for the refractive error of the eye 112 and thus makes the image quality as ideal as possible for the user 114. Thus, finally, the value of the refractive error of the user 114's eye 112 can be determined based on the contrast sensitivity function 160' of the user 114's eye 112, which can be for different spatial frequencies f fits the measurement value of the contrast sensitivity of the user 114's eye 112 to the best possible extent ε . However, other ways of acquiring and evaluating the measurement values can be envisioned.

[0153] In a particular embodiment, the defocus in at least two meridians can be determined. To this end, a periodic pattern 124 according to Figure 1 can preferably be represented on the visual display unit 120 first along a first direction 132 and subsequently along a second direction 134 (not shown), which second direction is preferably arranged perpendicular to the first direction 132 on the visual display unit 120. In this way, the vertex power values of one of the two principal meridians of the spherocylindrical spectacle lenses with astigmatism can be successively determined. For details in this regard, reference is made to WO 2018 / 077690 A1.

[0154] Figure 3 A flowchart of a preferred exemplary embodiment of a method 210 for determining the refractive error of a user 114's eye 112 according to the present invention is schematically shown.

[0155] In a representation step 212, to this end, according to step a), a symbol 122 is represented on the visual display unit 120, where the parameters of the symbol 122 represented on the visual display unit 120 are varied.

[0156] In an acquisition step 214, according to step b), an eye movement metric 144 of the user 114's eye 112 is acquired based on the symbol 122 represented on the visual display unit 120 according to the representation step 212.

[0157] In the establishing step 216, in accordance with step c), establish a time point that is apparent from the eye movement metrics of the eyes 112 of user 114 in the acquisition step 214 for the recognition threshold of the symbol 122 represented on the visual display unit 120, such that user 114 can just still recognize or just barely recognize the symbol 122 represented on the visual display unit 120 in accordance with the presenting step 212.

[0158] In the determining step 218, in accordance with step d), at the time point determined in the establishing step 216, determine the value 220 of the refractive error of the eyes 112 of user 114 according to the parameters defined for presenting the symbol 122 on the visual display unit 120 in the presenting step 212.

[0159] List of Reference Signs

[0160] 110 Device

[0161] 112 Eye

[0162] 114 User

[0163] 116 Mobile communication device

[0164] 118 Smart phone

[0165] 120 Visual display unit

[0166] 122 Symbol

[0167] 124 Pattern

[0168] 126 Maximum value

[0169] 128 Minimum value

[0170] 130 Spatial distance

[0171] 132 First direction

[0172] 134 Second direction

[0173] 136 Stripe

[0174] 138 Movement

[0175] 140 Camera

[0176] 142 Front camera

[0177] 144 Eye movement metrics

[0178] 146 Eye region

[0179] 148 Housing

[0180] 150 Evaluation unit

[0181] 152 Pupil

[0182] 154 Relative position of the pupil

[0183] 156 Pupil diameter

[0184] 158 Distance (interpupillary distance)

[0185] 160, 160'... Contrast sensitivity function

[0186] 162, 162'... Maximum point

[0187] 164, 164'... Region

[0188] 210 Method for determining the refractive error of a user's eye

[0189] 212 Representation step

[0190] 214 Acquisition step

[0191] 216 Establishment step

[0192] 218 Determination step

[0193] 220 Value of the refractive error of the user's eye

Claims

1. A computer-readable storage medium having stored thereon a computer program for determining the refractive error of one or both eyes (112) of a user (114), wherein, the computer program is configured to perform the following steps: a) Represent at least one symbol (122) on a visual display unit (120), wherein at least one parameter of the at least one symbol (122) represented on the visual display unit (120) is variable, and wherein the variation of the at least one parameter is represented on the visual display unit (120); b) When the at least one parameter varies, acquire an eye movement metric (144) of one or both eyes (112) of the user (114) based on the at least one symbol (122) represented on the visual display unit (120) by means of a camera (140); and c) Establish, by means of an evaluation unit (150), a time point of an identification threshold of the user (114) for the at least one symbol (122) represented on the visual display unit (120) that is apparent from the eye movement metric (144) of one or both eyes (112) of the user (114): the eye movement metric of the user just still follows or just begins to follow the movement of the at least one symbol represented on the visual display unit; characterized in that, d) Determine, by means of the evaluation unit (150), a value (220) of the refractive error of one or both eyes (112) of the user (114) according to the established time point.

2. The computer-readable storage medium according to claim 1, characterized in that, at least one parameter of the at least one symbol (122) represented on the visual display unit (120) is variable while the at least one symbol (122) represented on the visual display unit (120) moves (138) on the visual display unit (120).

3. The computer-readable storage medium according to claim 2, characterized in that, the movement (138) of the at least one symbol (122) represented on the visual display unit (120) is carried out continuously or in jumps.

4. The computer-readable storage medium according to any one of claims 2 to 3, characterized in that, the time point is established by means of the eye movement metric (144) in which the user (114) just still follows or just follows the movement (138) of the at least one symbol (122) represented on the visual display unit (120).

5. The computer-readable storage medium according to any one of claims 1 to 3, characterized in that, first determine the contrast sensitivity of one or both eyes (112) of the user (114) according to the at least one parameter established at the time point, and thereafter determine a value (220) of the refractive error of one or both eyes (112) of the user (114) according to the contrast sensitivity of one or both eyes (112) of the user (114).

6. The computer-readable storage medium according to claim 5, characterized in that, First, a contrast sensitivity function (160') is established, which is fitted to the determined value of the contrast sensitivity of one or both eyes (112) of the user (114); then, based on the established contrast sensitivity function (160'), the defocus of one or both eyes (112) of the user (114) is determined; and finally, based on the defocus of one or both eyes (112) of the user (114), the refractive error value (220) of one or both eyes (112) of the user (114) is determined.

7. The computer-readable storage medium according to any one of claims 1 to 3, wherein, the at least one symbol (122) is or includes at least one periodic pattern (124), wherein at least one parameter of the at least one pattern (124) represented on the visual display unit (120) is or includes at least one spatial frequency.

8. The computer-readable storage medium according to any one of claims 1 to 3, wherein, the at least one symbol (122) is first represented in a first direction (132) relative to the orientation of the visual display unit (120), and subsequently represented in a second direction (134) that has changed relative to the first direction (132).

9. The computer-readable storage medium according to any one of claims 1 to 3, wherein, additionally, the distance (158) between one or both eyes (112) of the user (114) and the visual display unit (120) is acquired.

10. The computer-readable storage medium according to any one of claims 1 to 3, wherein, the computer program is executed when the user (114) is wearing a pair of glasses.

11. A computer program product, comprising a computer program for determining the refractive error of one or both eyes (112) of a user (114), wherein, the computer program is configured to perform the following steps: a) Represent at least one symbol (122) on a visual display unit (120), wherein at least one parameter of the at least one symbol (122) represented on the visual display unit (120) is varied, and the variation of the at least one parameter is represented on the visual display unit (120); b) When the at least one parameter varies, acquire an eye movement metric (144) of one or both eyes (112) of the user (114) based on the at least one symbol (122) represented on the visual display unit (120) by a camera (140); and c) By an evaluation unit (150), establish the time point of the recognition threshold of the user (114) for the at least one symbol (122) represented on the visual display unit (120) from the eye movement metric (144) of one or both eyes (112) of the user (114) by virtue of the fact that the eye movement metric of the user just still follows or just starts to follow the movement of the at least one symbol represented on the visual display unit; wherein, d) The evaluation unit (150) determines the value of the refractive error (220) of one or both eyes (112) of the user (114) according to the established time point.

12. A method for manufacturing spectacle lenses, wherein, the manufacturing of the spectacle lenses is implemented by processing a lens blank or a semi-finished spectacle lens, wherein the lens blank or the semi-finished spectacle lens is processed based on refractive data and optionally centering data, wherein the refractive data and optionally the centering data include instructions for compensating for the refractive error of one or both eyes (112) of the user (114), and wherein the manufacturing of the spectacle lenses includes determining the refractive error of one or both eyes (112) of the user (114) according to the following steps: a) Representing at least one symbol (122) on a visual display unit (120), wherein at least one parameter of the at least one symbol (122) represented on the visual display unit (120) is variable, and wherein the change in the at least one parameter is represented on the visual display unit (120); b) When the at least one parameter changes, collecting the eye movement metrics (144) of one or both eyes (112) of the user (114) by a camera (140) based on the at least one symbol (122) represented on the visual display unit (120); and c) The evaluation unit (150) establishes the time point of the recognition threshold of the user (114) for the at least one symbol (122) represented on the visual display unit (120) from the eye movement metrics (144) of one or both eyes (112) of the user (114) by virtue of the fact that the eye movement metrics of the user just still follow or just start to follow the movement of the at least one symbol represented on the visual display unit; characterized in that d) The evaluation unit (150) determines the value of the refractive error (220) of one or both eyes (112) of the user (114) according to the established time point.

13. A device (110) for determining the refractive error of one or both eyes (112) of a user (114), wherein, the device comprises: - a visual display unit (120) configured to represent at least one symbol (122) and a change in at least one parameter of the at least one symbol (122); - at least one camera (140) configured to collect the eye movement metrics (144) of one or both eyes (112) of the user (114) based on the at least one symbol (122) represented on the visual display unit (120) when the at least one parameter changes; and - An evaluation unit (150) for establishing a time point at which a recognition threshold of the user (114) for the at least one symbol (122) represented on the visual display unit (120) is apparent from an eye movement metric (144) of one or both eyes (112) of the user (114), wherein the eye movement metric of the user just still follows or has just started to follow the movement of the at least one symbol represented on the visual display unit. Characterized in that the evaluation unit (150) is further configured to determine a value (220) of refractive error of one or both eyes (112) of the user (114) based on the established time point.

14. The device (110) according to claim 13, Characterized in that the device (110) further comprises means for acquiring a distance (158) between one or both eyes (112) of the user (114) and the visual display unit (120).

15. The device (110) according to any one of claims 13 to 14, Characterized in that the device (110) further comprises a light source (160) emitting in the infrared spectral range, and the camera (140) is sensitive to infrared rays.

Images