PROCEDURE FOR CHECKING THE EYES

Description

[0001] The invention relates to a method for checking the eyes of a subject using a vision testing system, wherein a display device of the vision testing system shows visualized vision test symbols to at least one eye of the subject, wherein a vision test is carried out with the visualization of the vision test symbols, in which the vision test symbols are embedded in an image reproduction of a real environmental situation, wherein the display device is controlled by a control unit of the vision testing system, and wherein the display device comprises a backlit screen.

[0002] Such vision testing systems are well-known and regularly used to conduct vision tests. While a subject's refractive values ​​can be objectively determined using an aberrometer, the refractive values ​​subjectively perceived as optimal by the subject may differ from the objectively determined refractive values. A discrepancy between objective and subjective refractive values ​​is observed, among other things, when subjective refractive values ​​are determined under mesopic or scotopic lighting conditions. In particular, the refractive values ​​determined objectively under twilight or night vision may differ from the refractive values ​​determined subjectively under the same lighting conditions.

[0003] To create these lighting conditions for an eye test, the test subject is presented with optotypes on a backlit screen, while simultaneously the screen luminance and ambient luminance are reduced. The room in which the eye test is conducted is darkened, and the background of the optotypes on the screen is also darkened to simulate the desired visual conditions of twilight or night vision. Furthermore, the display devices or screens have a control unit that allows an operator to control the display of optotypes on the screen. This control unit can, for example, be designed like a remote control. Depending on the type of screen, it may have linear or circular polarization.The screen's polarization is regularly used for vision tests in conjunction with a trial frame or phoropter. The camera device can be used, for example, to measure the eyes, although measurements are hardly possible in simulated twilight or night vision due to the lighting conditions.

[0004] Screens that can adjust their screen luminance or backlight luminance depending on the ambient luminance are already known. For example, some mobile phones have this function. In these known screens, an optoelectronic sensor measures the light incident on the sensor or the ambient luminance, and the screen luminance is controlled or adjusted accordingly via the screen's backlight. For example, if the ambient luminance increases, the screen luminance also increases, and vice versa. However, such adjustment devices have the disadvantage that the discrete electronic components of the adjustment device, such as the optoelectronic sensor, regularly exhibit a non-linear response curve.The adjustment of screen luminance to ambient luminance is therefore not proportional, but rather follows a function determined by the functions of the respective electronic components of the adjustment device. This non-linear function of the screen luminance adjustment to ambient luminance thus distorts the results of subjective refraction measurements under changing, varying lighting conditions.

[0005] A vision testing system with the features of the preamble of the independent claim is known from US Patent 2007 / 171363 A1. The vision testing system comprises an LCD monitor for displaying optotypes or other representations, such as images of animals. Adjacent to the LCD monitor is a mirror that interacts with a lighting device and a camera device, such that the eyes of a test subject looking at the LCD monitor can be illuminated with infrared light via the mirror and recorded by a camera. This is intended, among other things, to allow the determination of eye movement and pupil diameter. A camera or detector and IR light-emitting diodes, which form the camera device and the lighting device, are fixedly mounted below the screen.

[0006] WO 2008 / 113853 A1 describes a vision testing system comprising an LCD monitor and a device for calibrating the LCD monitor. The device includes at least two sensors capable of detecting ambient light intensity, screen brightness, and color. Furthermore, it is designed to adjust the screen brightness to the ambient light level. This is achieved through a self-calibration process, in which the screen brightness is adjusted using a sensor located directly in front of the screen.

[0007] Another vision testing system is known from DE 10 2014 223442 A1. It discloses an infrared-based eye examination using IR light sources and IR cameras for pupil measurement under different lighting conditions.

[0008] The present invention therefore aims to propose a method for checking the eyes of a subject using a vision testing system, which allows for faster and more accurate results in vision tests.

[0009] This problem is solved by a method having the features of claim 1.

[0010] In the inventive method for checking the eyes of a subject with a vision testing system, vision test symbols visualized by a display device of the vision testing system are shown to at least one eye of the subject, wherein a vision test is carried out with the visualization of the vision test symbols, in which the vision test symbols are embedded in an image reproduction of a real environmental situation, wherein the display device is controlled by a control unit of the vision testing system, wherein the display device comprises a backlit screen, wherein the display device has a lighting device with an infrared light source, wherein the display device has a camera device adapted for receiving infrared light, wherein the eyes of the subject are illuminated with infrared light by means of the infrared light source and recorded by means of the camera device independently of ambient lighting.wherein objectively measured refraction values ​​of the subject are transmitted to or entered into the control unit, wherein the control unit automatically selects the size of the visual acuity symbols to be displayed depending on the objective refraction values, wherein the visual acuity symbols are visualized in a size adapted to the objectively measured refraction values ​​of the subject, wherein a subjective verification of the objectively measured refraction values ​​is carried out.

[0011] According to the invention, a vision test is performed by visualizing the vision test symbols, in which the vision test symbols are embedded in an image representation of a test subject's real-world environment. The real-world environment can, for example, be a depiction of a landscape, from which a perspective view of the landscape is derived. The vision test symbols can be displayed within this landscape.

[0012] According to the invention, the visual acuity symbols are visualized in a size adapted to the objectively measured refractive values ​​of a test subject, whereby a subjective verification of the objectively measured refractive values ​​is performed. A direct comparison between objectively and subjectively measured refractive values ​​becomes possible when the visual acuity symbols are visualized in a size adapted to the objectively measured refractive values ​​of the test subject. For this purpose, it can be provided that the objectively measured refractive values ​​are transmitted to or entered into the control unit, whereby the control unit then automatically selects the size of the visual acuity symbols to be displayed depending on the objective refractive values.

[0013] The camera device allows for complete or partial recording of the subject's eyes across various spectra. The camera device can be a digital camera or a camera chip with a lens integrated into a screen frame. When recording the subject's eyes, the camera device can capture and measure, among other things, the pupil diameter as it changes with light exposure. This information can then be used in vision tests.

[0014] The infrared light source and illumination device allow the subject's eyes to be illuminated. Particularly when vision tests are performed under mesopic or scotopic lighting conditions, the reduced ambient light makes it difficult to photograph the subject's eyes for specific vision tests. The infrared light source allows the subject's eyes to be illuminated with infrared light, independent of ambient light, and photographed using a suitably adapted camera. This also advantageously avoids glare for the subject caused by illuminating the eyes with infrared light. The illumination device can also be configured to include multiple infrared light sources, such as IR LEDs. These infrared light sources can be positioned directly adjacent to the camera.Preferably, two infrared light sources can be positioned equidistant from the camera device, in the same plane as the subject's eyes. It is also possible to position infrared light sources within the display unit. This makes it possible to determine whether the refractive values ​​objectively measured during twilight or night vision differ from subjectively measured refractive values ​​obtained under the same lighting conditions and thus with the same pupil diameter. In principle, the screen can also be designed with, for example, linear or circular polarization, or with another device that can be used for image separation.

[0015] The camera device and / or the infrared light source can also be designed to be movable into a storage position within the display device or into a recording position outside the display device. Furthermore, the camera device and / or the infrared light source can be positioned on the screen, allowing the camera to be retracted into a storage position, for example, behind the screen, or moved to a recording position next to the screen as needed. Movement of the camera from the storage position to the recording position and back can be accomplished by a drive unit within the camera device. If a relatively large camera is used, a deflecting prism can be provided, allowing the camera to be positioned behind the screen in a space-saving manner.

[0016] The screen can include an adjustment device for adapting the screen luminance to an ambient luminance, wherein the adjustment device can include a measuring device for measuring the screen luminance. In particular, because the adjustment device can include the measuring device with which the screen luminance can be measured, it becomes possible to control the screen's backlight and thus its luminance. The measuring device allows for continuous verification that the measured screen luminance corresponds to a specified screen luminance at a given ambient luminance.If the measured screen luminance deviates from the expected screen luminance, the adjustment device can correct the screen luminance accordingly, so that the measured screen luminance matches the expected screen luminance. Consequently, regardless of the characteristic curves of discrete electronic components in the display device, the adjustment device can adapt the screen luminance to the ambient luminance proportionally or according to a linear characteristic curve. This allows for even more accurate vision tests due to the consistent display conditions of vision test symbols despite varying ambient luminance.

[0017] In one embodiment, the measuring device can include an optoelectronic sensor that may be arranged adjacent to or in front of a display area of ​​the screen, such that the screen luminance can be measured. The optoelectronic sensor can, for example, be arranged in a longitudinal side or corner of a frame of the screen, such that light emitted from the screen falls onto the optoelectronic sensor. The optoelectronic sensor can be arranged so that it is not directly in front of the display area of ​​the screen, but merely adjacent to it. Alternatively, the optoelectronic sensor can be arranged directly in front of the display area, at a distance from the display area, or directly adjacent to it.This arrangement of the optoelectronic sensor makes it possible to measure the screen luminance relatively accurately without the optoelectronic sensor being visually disruptive in front of the display surface.

[0018] The measuring device can include an additional optoelectronic sensor for measuring ambient luminance. This additional optoelectronic sensor can also be located within the screen frame or at another point on the display device. It is essential that light emitted from the screen does not fall onto the additional optoelectronic sensor, as this could distort the measurement result. This makes it possible to measure and control both the ambient luminance and the screen luminance accordingly.

[0019] The vision testing system can comprise a stationary distance test display unit, the display area of ​​which is designed for vision tests with a viewing distance of 3 m to 10 m, preferably 4 m to 8 m, and / or a portable near test display unit, the display area of ​​which is designed for vision tests with a viewing distance of 10 cm to 3 m, preferably 30 cm to 1 m. The distance test display unit can then be used to display vision test symbols for testing distance vision, and the near test display unit can be used to display vision test symbols for testing near vision. The vision testing system can comprise either the distance test display unit or the near test display unit, and optionally other display units, or both the distance test display unit and the near test display unit, and optionally other display units.The distance test display device can preferably be stationary at the viewing distance specified above, relative to the subject, or mounted on a wall. If the subject is positioned at a defined viewing distance relative to the distance test display device for the purpose of conducting vision tests, the viewing distance to the device can be precisely determined. Furthermore, the display area of ​​the distance test display device can be many times larger than that of the near test display device, as comparatively larger vision test symbols may be displayed on the distance test display device. Because the near test display device is portable, it can be held or positioned by an operator or the subject at virtually any distance within the viewing distance specified above, relative to the subject's eyes.This allows for corresponding vision tests to be performed at a wide range of viewing distances to the near-test display device. Both the distance-test display device and the near-test display device can be remotely controlled by an operator using the control unit.

[0020] The control unit can be a mobile phone or a tablet computer. These control units have a touchscreen that allows an operator to conveniently select different vision tests or visual acuity symbols and assign them to the display device. Furthermore, the control unit can be programmed to fully control the display device; that is, the display device then only serves to show the visual acuity symbols initiated by the control unit. Independently of the display device, changes to the visual acuity symbols or new vision tests can be uploaded to the control unit via a software update, without requiring an update to the display device itself. The control unit can communicate wirelessly with the display device via Wi-Fi or Bluetooth.However, the control unit can also be a permanently installed computer or a laptop on which software for controlling the display device can be run.

[0021] Furthermore, the display device may include a glare device by means of which the subject's eyes can be illuminated. The glare device may comprise at least one light source located adjacent to the screen. For example, the light source may be a light-emitting diode (LED). The light source may be integrated into a frame of the display device. It may also be provided that a light source of the glare device is arranged on each long side of the display device's screen.

[0022] The vision testing system can include a phoropter or a trial frame. This makes it possible to determine the refraction of each subject's eyes individually. The phoropter or trial frame can also have color filters or polarization filters, each adapted to a specific color representation and / or polarization of the screen, allowing for monocular and binocular vision tests. For example, if a phoropter or trial frame with linear or circular polarization is already available, the display device of the vision testing system can be selected to be polarized to match the phoropter or trial frame. A polarization correction, such as with a λ / 4 filter, is therefore unnecessary.

[0023] Furthermore, the vision testing system can include a building automation system for lighting control, which can be operated via the control unit. This building automation system could be, for example, an electrically operated blind, a roller shutter, and / or artificial lighting in the room where the vision testing system is used. For instance, the control unit can then be used to open or close a roller shutter or to control the brightness of the interior lighting. Control of the building automation system via the control unit can be achieved, for example, via Wi-Fi or Bluetooth, allowing an operator to conveniently adjust the lighting conditions in the examination room for specific vision tests while operating the display device.Among other things, it may also be provided that when a specific vision test is selected by an operator at the control unit, the building services equipment is automatically controlled by the control unit to adjust the lighting conditions to the vision test.

[0024] In principle, the screen can also be designed, for example, with linear or circular polarization, or with another device that can be used for image separation. For the advantages of the method according to the invention, reference is made to the description of advantages of the vision testing system according to the invention.

[0025] Using a camera on the display device, the pupil diameter can be measured, allowing for a vision test to be performed on a subject under twilight or night vision conditions. Only then, by illuminating the pupils with infrared light via a lighting device, is it possible to measure the pupil diameter and determine a subjective refraction under mesopic or scotopic visual conditions. The subjective refraction values ​​can then be compared with objective refraction values ​​measured at essentially the same pupil diameter. The objective refraction values ​​can, for example, be automatically transmitted from a measuring device to the vision testing system.

[0026] Furthermore, the screen luminance can be adjusted to the ambient luminance, whereby the adjustment of the screen luminance can be proportional to the ambient luminance. In this method, the screen luminance is adjusted to the ambient luminance using an adjustment device such that the relationship between screen luminance and ambient luminance is always linear.

[0027] In one embodiment of the method, the screen luminance and color reproduction of a display area can be measured by an optoelectronic sensor and controlled by an adjustment device on the screen. Vision tests requiring a defined representation of color or contrast for vision test symbols can then be performed with exceptional accuracy. The adjustment device can automatically control the screen luminance and / or color reproduction, allowing the screen to self-calibrate. The screen can be, for example, the screen of a tablet computer or a conventional television. Vision test symbols can be displayed with a screen backlight of 90 to 300 cd / m².While it is possible to display the vision test symbols in grayscale, it is not necessary, as the screen luminance can be easily adjusted via the backlight control.

[0028] Using the display device's camera, the interpupillary distance, pupil diameter, measuring distance, head tilt, and / or gaze direction of the subject's eyes can be captured and measured. If the subject's viewing distance to the screen is known in principle due to the fixed positioning of both the screen and the subject, the interpupillary distance can be calculated from an image of both eyes captured by the camera device or a camera using image processing. A relative distance between the pupils can be used, for example, to fit eyeglasses or to administer specific vision tests. The pupil diameter can also be measured in this way depending on the ambient lighting. Conversely, if the interpupillary distance is known, a measuring distance or viewing distance of the subject relative to the screen can be calculated from an image captured by the camera device using image processing.It is also possible to record the subject's head tilt relative to the screen as well as the direction of gaze or fixation on visual acuity test symbols.

[0029] It is therefore particularly advantageous if the display device's orientation sensor can measure the screen's position, especially its tilt, relative to the subject's eyes. The orientation sensor can be a gyroscopic sensor, which allows the spatial position or orientation of the screen or display surface to be determined. For example, if the subject's eyes or head are captured with a camera on the display device, the screen's tilt relative to the eyes can be easily calculated using a known interpupillary distance. The screen can then indicate that it is tilted relative to the eyes and, for example, that an eye test cannot be performed. The screen can also display information on the correct orientation of the screen relative to the subject's eyes.The test subject may then be able to position the screen relative to their eyes in the position required for a vision test.

[0030] The display device's camera allows for continuous eye tracking of the subject. This enables the calculation of a fixation point on the screen's display area. This is possible when the subject's eye direction is recorded. In this way, vision tests can be used to examine the extent to which the subject dynamically tracks monocularly or binocularly presented visual acuity targets.

[0031] When continuous eye tracking is performed for presented visual acuity tests, monocular and / or binocular visual acuity can be determined from the interplay between eye movement and test position. This so-called eye-tracking can also be used, for example, when reading text displayed on a screen.

[0032] If a viewing distance or measuring distance is known, the vision test symbols can be displayed in a size adapted to that distance. The display of these size-adjusted vision test symbols can be automated or manual via the control unit or by an operator. This ensures that the vision test symbols are always displayed in the required size and prevents errors during vision tests.

[0033] The vision testing system can comprise a stationary distance test display unit and a portable near test display unit. A pupillary distance and / or pupil diameter measured with the distance test display unit can be used in a measurement with the near test display unit. If a subject is positioned in front of the distance test display unit at a defined viewing or measurement distance, the measurement distance is then known. The subject's pupillary distance can then be measured using a camera device on the display unit. With a known measurement distance, the pupillary distance can be determined from a camera image using image processing. Similarly, it is possible to determine an illumination-dependent pupillary diameter in this way. The pupillary distance and / or pupillary diameter can be used in a measurement with the near test display unit to determine the measurement distance or...The viewing distance between a subject's eyes and the screen of the near-vision display device is calculated. If the near-vision display device also has a camera, image processing can be used to capture the subject's pupillary distance or pupil diameter from the camera image and compare it to the pupillary distance and pupil diameter measured by the distance-vision display device. This allows the measurement distance to be calculated in relation to the image captured by the near-vision display device or its camera. Such calculations can be performed, for example, using triangulation and executed by the control unit. The display of vision test symbols can then always be based on the actual measurement distance of the near-vision display device.

[0034] The measuring distance of a subject's eyes relative to the screen of the near-vision display device can be determined even more precisely if the pupillary distance measured with the distance-vision display device at a known measuring distance is used for distance measurement with a camera device of the near-vision display device, taking into account the convergence of the eyes. Since, with the near-vision display device, test symbols may no longer be viewed at infinity at measuring distances of 10 cm to 3 m, the subject's eyes then focus on a test symbol presented on the screen of the near-vision display device. The gaze axes of the eyes are essentially convergent in this process. This results in a reduced pupillary distance compared to a distance-vision test or when looking at infinity, which can be taken into account when calculating a measuring distance and / or conducting vision tests.

[0035] Visualizing the visual acuity symbols allows for a vision test to be performed, determining a subject's eye deviation, monocular vision, binocular vision, daytime vision, twilight vision, or night vision. Eye deviation can be determined, for example, using the Maddox or Thorington vision tests. Monocular and binocular vision can be assessed by determining the refraction of the eyes, sometimes in conjunction with a trial frame or phoropter. In addition to conducting vision tests under photopic lighting conditions, mesopic or scotopic lighting conditions can also be set to test and determine a subject's twilight and night vision. This involves, in particular, reducing the screen luminance and ambient luminance to create mesopic or scotopic viewing conditions.For example, so-called night glasses can then be fitted to the subject with dilated pupils.

[0036] Subjective verification of objectively measured refraction values ​​can be performed taking pupil diameter into account. Since the objectively measured refraction values ​​may have been determined under uniform lighting conditions with, for example, a small pupil diameter using an aberrometer, the screen luminance and ambient luminance can be reduced during subjective verification to such an extent that the pupil diameter becomes comparatively larger. This may result in subjectively measured refraction values ​​that differ from the objectively measured values.

[0037] Visualizing the visual acuity symbols allows for the determination of a subject's phoria. The phoria can be identified solely by the relative displacement of at least one visual acuity symbol perceptible only to the right eye and at least one visual acuity symbol perceptible only to the left eye. Dissociated phoria can be determined using a Maddox or Thorington vision test. This can involve using light sources such as LEDs positioned outside the screen, for example, within a frame of the display device, in conjunction with a scale displayed on the screen. Alternatively, by using a trial frame or a phoropter with a polarizing filter, a phoria can be determined by relative displacement without the need for prisms, provided that the visual acuity symbols are perceptible and movable separately by the right and left eyes.

[0038] Furthermore, the environmental situation can be a traffic situation in sunshine, fog, rain, twilight, or night, with or without artificial lighting. For example, a vehicle on a road can be depicted, with visual acuity markings embedded in the license plate. The image can then be enlarged or reduced to simulate a greater subjective viewing distance to the depicted environment or vehicle. This makes it easy to check, for instance, whether a test subject is still able to recognize the vehicle's license plate from a freely selectable distance. This vision test can be varied with different lighting conditions, as described above.

[0039] Vehicle lights can also be depicted, allowing color vision deficiency to be determined by varying a single hue of the lights. The vehicle lights could be, for example, taillights or brake lights, so that a single hue is varied independently. For instance, the hue could be a shade of red, allowing the perception of this hue to be bridged by two differently varied lights.

[0040] The environmental situation can also be displayed in three dimensions. For example, the screen can be a conventional television set suitable for three-dimensional display when used with polarized glasses or trial glasses with a polarization filter. However, it is also possible to display the environmental situation in two dimensions. It is particularly advantageous to use a screen capable of displaying the environmental situation and / or the vision test markings in 4K format.

[0041] Further embodiments of the method are set out in the dependent claims relating to device claim 1.

[0042] A preferred embodiment of the invention is explained in more detail below with reference to the accompanying drawings.

[0043] They show: Fig. 1 a schematic representation of an embodiment of a vision testing system; Fig. 2 A schematic representation of the arrangement of a vision testing system.

[0044] The Fig. 1 Figure 10 shows a vision testing system 10 comprising a distance test display unit 11, another distance test display unit 12, and a near test display unit 13, as well as a control unit 14 for controlling the display units 11, 12, and 13, respectively. The vision testing system 10 further includes a roller shutter control unit 15 with a roller shutter 16 and a controllable light source 17 in a room not shown here. The roller shutter control unit 15 and the light source 17 are also controllable by the control unit 14. The display units 11, 12, and 13, as well as the roller shutter control unit 15 and the light source 17, are connected to the control unit 14 via a WLAN network 18 for data exchange. The distance test display unit 11 consists of a screen 19 with a frame 20. The screen 19 is backlit and can be linearly or circularly polarized. Light-emitting diodes 23 are integrated into the longitudinal sides 21 and 22 of the frame 20, which together form a glare shield 24.The light-emitting diodes 23 illuminate the eyes of a test subject in such a way as to produce a glare effect. The remote test display device 11 further comprises a camera device 25 and a lighting device 26 with infrared light-emitting diodes 27. The camera device 25, together with the lighting device 26, can be lowered into the frame 20 by a motor. A display area 28 of the screen 11 is comparatively larger than a display area 29 of a screen 30 of the remote test display device 12. The remote test display device 11 can therefore be used for comparatively greater measurement distances or viewing distances for vision tests than the remote test display device 12.

[0045] The near-test display device 13 also has a camera device 31 in a frame 32 and a light-emitting diode 33 that forms a glare shield 34. The display area 36 of a screen 35 of the near-test display device 13 is comparatively small compared to the display area 29 of the distance-test display device 12. Optometry symbols or vision tests, not shown here, can be selectively displayed on the respective display areas 28, 29, and 36 via the control unit 14. Furthermore, the display devices 11, 12, and 13 each have optoelectronic sensors 37 arranged in a corner 38, 39, and 40 of the frames 20, 32, and 41, respectively. The optoelectronic sensors 37 are part of a measuring device, not shown in detail here, which measures the screen luminance of the screens 19, 30, and 35, respectively, as well as the ambient luminance of a room.The ambient luminance is measured by means of an optoelectronic sensor (not shown) integrated into frames 20, 32, and 41, respectively. The screen luminance is then adjusted proportionally to the ambient luminance by means of the control unit 14 or the display unit 11, 12, or 13. The ambient luminance, in turn, can be adjusted manually or automatically via the control unit 14 by manipulating the roller shutter 16 and the light source 17.

[0046] The Fig. 2Figure 42 shows a vision testing system 42 in a room 43 together with a test subject 44. The vision testing system 42 comprises a distance test display unit 45 and a near test display unit 46, as well as a trial frame 47, which the test subject 44 wears. The distance test display unit 45 is fixed to a wall 48, and the near test display unit 46 is held manually by the test subject 44. Furthermore, the room 43 is equipped with a light source 49, which allows for control of the ambient luminance. Using a control unit of the vision testing system 42 (not shown here), an operator can perform a vision test with the test subject 44 by displaying vision test symbols on the distance test display unit 45, which is located at a relatively large measuring distance relative to the test subject 44. The near test display device 46 can be handled by the subject 44 himself, whereby the measuring distance between the subject 44 and the near test display device 46 is comparatively smaller.Here too, if required, the subject can be presented with visual acuity test symbols via the control unit.

Claims

1. A method for testing the eyes of a subject by means of a vision testing system (10, 42), optotypes visualized to at least one eye of the subject (44) being displayed by means of a display device (11, 12, 13, 45, 46) of the vision testing system, an eyesight test being performed by visualizing the optotype, in which the optotypes are embedded in an image replication of a real environmental situation, the display device being controlled by means of a control device (14) of the vision testing system, the display device comprising a backlit screen (19, 30, 35), the display device having an illuminating device (26) comprising an infrared light source (27), the display device having a camera device (25, 31) correspondingly adapted to the infrared light source, eyes of the subject being illuminated with infrared light by means of the infrared light source and captured by means of the camera device independently of an ambient illumination, objectively measured refraction values of the subject being transmitted to the control device or entered into the same, the control device automatically selecting the size of the optotypes to be displayed as a function of the objective refraction values, the optotypes being visualized in a size that is adapted to the objectively measured refraction values of the subject, the objectively measured refraction values being subjectively reviewed.

2. The method according to claim 1, characterized in that a pupillary distance is measured by means of the camera device (25, 31) of the display device (11, 12, 13, 45, 46), an eyesight test being performed under mesopic vision or scotopic vision of a subject (44).

3. The method according to claim 1 or 2, characterized in that a screen luminance of the screen is adjusted to an ambient luminance, the screen luminance being adjusted proportionally as a function of the ambient luminance.

4. The method according to any one of claims 1 to 3, characterized in that a pupillary distance, a pupil diameter, a measuring distance, a head tilt and / or a line of sight of the eyes of the subject (44) is registered and measured by means of the camera device (25, 31) of the display device (11, 12, 13, 45, 46).

5. The method according to any one of claims 1 to 4, characterized in that a position, in particular a tilt of the screen (19, 30, 35) relative to the eyes of the subject (44) is measured by means of a position sensor of the display device (11, 12, 13, 45, 46).

6. The method according to any one of claims 1 to 5, characterized in that the eyes of the subject (44) are continuously tracked by means of the camera device (25, 31) of the display device (11, 12, 13, 45, 46).

7. The method according to claim 6, characterized in that the continuous eye tracking takes place for presented optotypes, a monocular and / or binocular visual performance being determined from an interrelation between eye movement and optotype position.

8. The method according to any one of claims 1 to 7, characterized in that the optotypes are presented in a size adjusted to the measuring distance.

9. The method according to any one of claims 1 to 8, characterized in that for a display device, the vision testing system (10, 42) has a stationary distance-test display device (11, 12, 45) and a mobile near-test display device (13, 46), a pupillary distance and / or a pupil diameter measured with the distance-test display device being used when measuring with the near-test display device.

10. The method according to claim 9, characterized in that the pupillary distance measured with the distance-test display device (11, 12, 45) at a known measuring distance is used for distance measuring with the camera device (31) of the near-test display device (13, 46), a convergence of the eyes being taken into account.

11. The method according to any one of claims 1 to 10, characterized in that an eyesight test is performed by visualizing the optotypes, the eyesight test determining eye offset, monocular vision, binocular vision, photopic vision, mesopic vision or scotopic vision of a subject (44).

12. The method according to any one of claims 1 to 11, characterized in that the objectively measured refraction values are subjectively reviewed, the review taking a pupil diameter into account.

13. The method according to any one of claims 1 to 12, characterized in that by visualizing the optotypes, a phoria of a subject (44) is determined, the phoria being determined solely by shifting at least one optotype visible the right eye alone and by shifting at least one optotype visible to the left eye alone relative to each other.

14. The method according to any one of claims 1 to 13, characterized in that the environmental situation is a traffic situation in sunshine, fog, rain, twilight or at night with and without display of artificial lighting.

15. The method according to any one of claims 1 to 14, characterized in that the lights of a vehicle are shown, a color vision deficiency being determined by varying a shade of color of the lights.