DE29517990U1 - Device for testing visual functions - Google Patents

Description

Device for testing visual functions

The invention relates to a device according to the preamble of claim 1. Such devices are used to test visual field defects or changes in the perception threshold per retinal location under various boundary conditions, e.g. in examination tests such as perimetry or noise field campimetry. Furthermore, the device enables the measurement of visual acuity for distance and near depending on the ambient brightness, measurement of night vision under realistic conditions with glare, such as those that occur in traffic, color tests under adaptation conditions and stereometric tests using a binocular display as well as squint tests with squint angle determination.

The methods for measuring the visual field are perimetry, campimetry or noise field campimetry. Perimetry determines the light sensitivity of any desired point in the retina. The device used is usually an arrangement in the form of a sphere perimeter according to Goldmann etc. The test subject fixates on a fixation point presented in the center of the sphere. Light markers are briefly presented to him at various locations within the sphere. When recognized, a signal is triggered. Today, computer-controlled perimeters are mostly used. The computer controls the projection of the test markers with a location-dependent light intensity according to the physiological perception threshold of the retina at various locations within the hemisphere.

The method is also used in the form of campimetry. Here, only the 30° to 60° field of vision is tested using a video monitor. This type of test is known, for example, from patent US 4,634,243. In campimetry, the patient fixates on a video monitor at a defined distance, using the same principle.

Noise field campimetry, as disclosed in EP 88112691.6, for example, presents a noise field on the display screen in the manner of a television picture "without reception". By observing this noise field, the test subject can perceive any failures as a failure of the noise field.

From the published patent application EP 0 363 610 A1, the projection of test marks via a computer-controlled electromechanically deflectable projector consisting of a light source, aperture and lens is known, whereby a certain miniaturization of the perimetric test method is made possible by the fact that an optical imaging system with magnification properties is arranged between the light source and the observer position.

A device is known for testing visual acuity (US 4 869 589) in which optotypes are displayed on a computer-controlled monitor. The test is automated, and the patient can report his or her reaction to the system using a keyboard or mouse.

Portable viewing table devices are known for examining twilight vision and glare sensitivity, e.g. from DE 30 03 588 C2.

Examination devices in the form of glasses are known for measuring eye movements, such as for measuring nystagmus, see e.g. DE 38 25 789 C2 and EP 0 456 166 Al.

The problem with the systems used to test visual functions is that they are very large in terms of their spatial extent and, because various testing devices are connected to a complex arrangement of examiner screen, computer control, etc., they are also very expensive. In the perimeter, the cupola alone has a diameter of between 60 cm and 100 cm.

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The campimeters are also very large systems due to monitors, computer controls and distance devices in the form of chin and forehead rests. Refractometers and other table devices, usually based on an optical lens and mirror system, are available for testing visual acuity. The angle of the squint is determined using compensating prism glasses or on a 2.5m*2.5m Harms wall. The majority of the devices are very specific to the examination and are therefore only suitable for one or a few special examinations, so that additional devices must be purchased for further examinations. Some systems can only be operated in darkened rooms with room brightness that is not or only with difficulty adjustable, so that boundary conditions such as room brightness cannot be standardized and therefore cannot be reproduced precisely.

The technical problem of the invention is to create a device of the type mentioned at the beginning, which detects visual field defects at least in the 30° to 60° visual field and is very compact. A further aim is to realize such a device in such a way that subjective examinations, such as the determination of the angle of strabismus, can be objectified and vision tests can be standardized with defined contrast and room brightness. Furthermore, different examinations, each of which previously required a separate device, should be able to be carried out with just one such device.

This problem is solved by a device with the features of claim 1. By using a retinal projection device (Virtual Retina Display) according to claim 1 in conjunction with an optical imaging system, a very compact structure is made possible. This is exploited in order to be able to accommodate the entire optical part of the device in a glasses- and/or helmet-like carrier that can be attached to the test subject, making the device very mobile and universally applicable.

By adding additional sensory components, special lighting and a light-tight design, the functions of previously different devices are combined and standardized. Particularly advantageous developments of this type are specified in the subclaims.

The examination of the visual field can be combined with other examinations, such as checking perception during dark adaptation, measuring visual acuity at a distance or close up, measuring the reaction speed of a test subject to an optical stimulus, determining squint angles, testing night vision under traffic conditions with glare from the backlight, and color tests and stereometric tests. If two lasers are used for interferometric projection, the above-mentioned examinations can also be carried out better on older patients with corresponding lens opacities. The invention thus combines various examination devices in the miniaturized form of glasses or a helmet or a table device and the like. The control of the device should be able to be connected to personal computer systems, preferably in conjunction with a plug-in card, in order to reduce costs and save space.

A further advantage of the invention is that the room in which the examinations are to be carried out does not have to be darkened as with conventional methods, but the examinations can take place in daylight under standardized brightness conditions.

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In the following, the invention is explained in more detail with reference to drawings showing a preferred embodiment, in which:

Fig. 1 is a schematic block diagram of a device for testing several visual functions and

Fig. 2 is a schematic plan view of the optical part of the

Device of Fig. 1.
Fig. 3 a schematic representation of the functionality of a Virtual Retina Display

The device is first explained using Fig. 1. The optical device part (8) is in the form of a pair of glasses or a small table device, the structure of which is described in more detail using Fig. 2 below, and consists of a virtual retina display (9), a photoresistor (13), a sensor (10) for measuring the position of the eyes and light sources for regulating a glare device (lla/llb) and for regulating the brightness inside the glasses (11, 8), whereby the virtual retina display (9) can be connected to a computer (1) via a driver (5) and the other units (10, 11, 11a, 11b, 13, 14) of the glasses (8) can be connected to a computer (1) via an A/D (D/A) converter (6). The optotypes or images are generated in the computer (1) by the software and displayed on the virtual retina display (9) via the driver (5). The computer software controls the shape, size, appearance time, brightness and color of optotypes and background as well as their location on the Virtual Retina Display.

To test the visual field, the subject is first presented with a fixation optotype, usually located in the center of the Virtual Retina Display (9).

The fixation mark is the reference point for specifying the angle of other test marks shown on the Virtual Retina Display (9) during the course of the examination and its location is specified as 0 degrees. While the test subject fixates on this point, optotypes (test marks) are presented according to the principle of grid perimetry, static perimetry or dynamic perimetry, the location and brightness of which are controlled by the computer (1). If the test subject perceives an optotype, he or she activates a signal generator (12). The signal generator (12) can transmit the signal via an A/D converter or, as described here, via a keyboard (7). The computer (1) stores the signal with the associated location (angle of view) and intensity of the optotype being tested in a memory (4). Fixation control is carried out via the sensor (10). According to the specified characteristics, the optotypes can be presented even in the case of an unconventional or incorrect fixation, since the projection location of the optotypes can be corrected by measuring the position of the eyes in real time using the sensor (10). The examiner can follow the current status of the examination or influence the course of the examination on an examiner monitor (3). The examiner controls the entire examination process using the associated software. The keyboard (7) is used for input by the examiner. He is also able to control the brightness inside the glasses (8) and the brightness of the glare device (11a, lib). A photoresistor (13) measures the brightness inside the glasses and sends the signal back to the computer (1) via the A/D converter (6). Conversely, the brightness of the interior lighting is controlled by the computer (1) via the A/D or D/A converter (6). All measured values are constantly displayed on the examiner's monitor (3). The determined data can then be output in a standardized manner via a printer (2) or another output device or stored in a memory (4). It is also possible to store the measured data directly in the computer (1) using algorithms,

Fuzzy logic or similar diagnostic aids can be used to further process data. In this way, comparative values for previous studies can be determined directly or measured values can be analyzed and output directly.

Fig. 2 shows a systematic representation of the measuring glasses/table device (8) itself. The optical media are drawn along the optical axis (29). The test subject looks at the Virtual Retina Display (9) through a corresponding eyepiece (28) and an associated field lens (27). These elements can be moved electrically or manually to compensate for any refraction anomalies of the test subject or to display the image or optotype under distance vision conditions or near accommodation. In addition, additional lenses can be inserted. The resulting change in the angle of view is taken into account in the control system. The brightness of the Virtual Retina Display (9) can be controlled by the examiner by controlling the Virtual Retina Display (9) accordingly. The Virtual Retina Display (9) is able to display discrete grayscale or color levels. The pixels themselves as well as combinations of pixels (images, optotypes, etc.) can be controlled. The backlight glare (11a/lib) is made up of a light source, a reflector (31a) and an associated lens (31) to focus the light beam. To enable backlight glare, the glare unit (11a/lib) can either be placed directly in front of the Virtual Retina Display (11b, 9) or installed behind the display (Ha, 9). The glare can alternatively be reflected via the semi-transparent mirror (33). The brightness inside the glasses can be regulated via additional lighting units (11) and an associated diffuser (24). If required, a color filter can be placed between this lighting source (11) and the diffuser (24). A photoresistor (13) measures the brightness inside the glasses.

Furthermore, the sensor (10) measures the position of the eye(s) in real time and reports the result to the computer (1) via the converter (6). The sensor (10) can be attached to or in front of the eyepiece (28) or can be reflected via a semi-transparent mirror. It is used to measure the position of the test subject's eyes. If required, a camera system for displaying the eye can also be reflected via the semi-transparent mirror (33). The entire unit is sealed off from the outside in a light-tight manner. The transition from the test subject to the measuring glasses is made possible by an elastic cuff (30).

Fig. 3 shows a schematic of the possible structure of the retina projection device (Virtual Retina Display). One or more lasers (40) are directed to rotating mirrors (43/44) via deflecting mirrors (41) and corresponding lenses. One of the rotating mirrors deflects the laser radiation in a horizontal direction and one in a vertical direction. This allows the laser light to be projected onto the retina of an eye (46) in a planar manner and focused using optics (45/27/28). The deflecting mirrors can be rotated so quickly that the eye has the impression of a planar image. The color and brightness of the laser light can be defined for each mirror position, so that an image can be projected onto the retina as a whole.

In addition to the visual field measurement described above, the device enables the following additional visual function tests, whereby, as required, one or more of the components specified in the subclaims are provided in addition to the components explicitly shown.

By equipping the device with the features according to claims 8 and/or 9, a noise field can be displayed on the Virtual Retina Display (9) in order to make scotomas immediately visible to the subject.

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To test visual acuity, the test subject is presented with visual symbols of different sizes and shapes with high contrast at a defined internal brightness. The test subject reports what he saw to the examiner. The examiner compares the results with those of his monitor (3). By equipping the device with the features according to claim 7, the image for testing visual acuity can be presented near or far via the optical imaging system (27, 28) by moving or exchanging the optical system. Due to the possibility of motor adjustment, the test subject can, with the help of two signal transmitters, which in this case move the optics, specify the range of adjustment options that still provides a sharp image for him under different accommodation conditions (accommodation range).

Furthermore, according to the features of claim 11, the visual acuity test can be carried out under backlight glare (mesoptometry). The test subject is blinded with a focused light cone. The blinding device (Ha) can be located behind the display (9). The media to be penetrated are obvious to the person skilled in the art, e.g. realized by a suitable light passage opening in the diffuser (22) and the display (9). Furthermore, the blinding device (Hb) can be installed in front of the virtual retina display (9), or the blinding light can be reflected via a semi-transparent mirror (33), which is optionally shown in Fig. 2.

To test the reaction time, the test subject is briefly presented with visual symbols. The computer (1) measures the time from the presentation on the device's virtual retina display (9) to the test subject's reaction via the signal generator (12). The conditions under which a reaction should occur can be agreed in advance, etc.

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To examine squint or determine the angle of squint, the position of the eyes relative to one another in different viewing directions is checked with a sensor (10) or a so-called eye tracking system by equipping the device with the features according to claim 5. The viewing directions are specified by a fixation symbol on the display screen (9). This is possible for distance and near vision when the device is equipped with the features according to claim 4. According to the so-called cover test, the viewing direction and position of the eyes can be checked with a short alternating sequence of stimuli.

In the case of the implementation of the device according to claim 10, the device is monocular, i.e. only one side contains the actual part of the device that tests the visual function, while the other side contains a brightness-adjustable space according to claim 4, which, depending on the design, is equipped with individual components as mentioned in claims 1 to 12. In this case, the device can be used alternately by rotating or swapping the two sides. The binocular design contains the complete part of the device that tests the visual function on both sides.

According to claims 7, 8 and/or 9, images or optotypes with different levels of disparity are presented for stereo tests in binocular execution. This is possible for distance and near vision according to claim 4. The test subject must then, for example, identify spatially prominent optotypes, symbols or image content as the disparity decreases.

To test color discrimination, the test subject is presented with one half of the screen with a given color and brightness per eye according to claims 8 and/or 9. The test subject can adjust the other half of the screen to the given one using the two signal generators. Furthermore, different

Color levels are offered which the test subject has to sort. This can be done using the two signal generators. Furthermore, pictures in the form of Ishahara tables can be offered.

With a further development of the invention according to claims 3, 4, 8, 9 and/or 10, the roughness and/or the brightness of the optotypes to be identified can be changed over time in order to test the dark/light adaptation.

With a further development of the Virtual Retina Display according to claim 13, the visual function tests can be carried out interferometrically in order to better penetrate lens opacities in the eye of older patients.

All functions of the device are controlled via the associated software and can be varied in terms of their execution options.

The advantages achieved by the invention are that the design of the device creates a small, handy measuring device in contrast to the large, known systems. The combination of the possible measuring processes enables the functions of several systems to be concentrated on a single device that records the essential visual functions (field of vision, visual acuity, interference vision, night vision, reaction to optical impressions), such as those required when driving a car. The design with inexpensive elements and the use of existing elements (computer) makes it possible to integrate the system into existing systems, which leads to a significant reduction in costs and space savings. The problem-free use in normal daylight makes operation uncomplicated and convenient. The device can also be used in conjunction with a video camera as an image intensifier for the visually impaired.

Claims (13)

m sayings 1. Device for testing at least one visual function in the eye of a subject with - an optical device part (8) which includes a retinal projection device consisting at least of a coherent light source such as a laser and a deflection mirror and a lens arrangement (9) for presenting optical symbols and images at different angles measured to the optical axis (29), and a computer control (1, 5) for controlling the retina projection device (9),
characterized in that the optical device part (8) is housed in a table device or a spectacle-like and/or helmet-like carrier (8) that can be attached to the test subject and contains an optical imaging system (27, 28) in front of the retinal projection device (9). 2. Device according to claim 1, further characterized by at least one signal generator (12) operable by the subject, which is connected to the computer control (1). 3. Device according to claim 1 or 2, further characterized in that the table device or the spectacle-like and/or helmet-like carrier encloses the space between the display screen (9) and the viewing position (30) in a light-tight manner. 4. Device according to claim 3, further characterized by a controllable lighting device (11) and a brightness sensor (13) which are connected to the computer control (1) for adjusting the brightness and color of the light-tight room. 5. Device according to one of claims 1 to 4, further characterized by a device for measuring the eye position and eye movements (10). 6. Device according to one of claims 1 to 5, further characterized in that the computer control includes a computer (1) for measuring, evaluating and controlling the examinations perimetry, noise field campimetry, mesoptometry, distance visual acuity, near visual acuity, accommodation range, stereo tests, squint angle determination, dark adaptation, reaction ability and/or color recognition. 7. Device according to one of claims 1 to 6, further characterized in that the optical imaging system (27, 28) for focusing the retinal projection device on an area located in front of the observer point (30) and occupable by the retina of the eye of a subject is manually or motor-adjustable or replaceable and the optics for the virtual optical imaging are adjustable or replaceable at different distances for examination during distance vision and near accommodation. 8. Device according to one of claims 1 to 7, further characterized in that the retinal projection device consists of at least one laser with discrete color levels or brightnesses and the mirrors are movable at a high frequency and brightness and color can be regulated in every position. 9. Device according to one of claims 1 to 8, further characterized in that it is designed monocularly and a light-tight enclosed space, the brightness of which can be adjusted by means of a lighting device, is provided for the eye not being examined, the functional units being interchangeable between the right and left eye. 10. Device according to one of claims 1 to 9, further characterized by a glare device with a light beam bundled by an optical system (11a, lib), which can be directed at one or both eyes at a specific angle, whereby the glare device can be inserted or mirrored behind the display (11a, 9) or in front of the Virtual Retina Display (11b, 9). 11. Device according to one of claims 1 to 10, further characterized in that glare and/or a measuring system or an imaging camera system for measuring the position of the eyes can be reflected via a semi-transparent mirror (33). 12. Device according to one of claims 1 to 11, further characterized in that by combining several lasers, different color mixtures can be projected onto the retina at any mirror position and brightness 13. Device according to one of claims 1 to 12, further characterized in that by combining several lasers interference patterns or interference images can be projected onto the retina.