WO1998051206A1

WO1998051206A1 - Device for detecting and indicating defective vision in human beings

Info

Publication number: WO1998051206A1
Application number: PCT/EP1998/002742
Authority: WO
Inventors: Frank Schaeffel; Stefan Weiss; Eberhart Zrenner
Original assignee: Eberhard-Karls-Universität Tübingen Universitätsklinikum
Priority date: 1997-05-09
Filing date: 1998-05-11
Publication date: 1998-11-19
Also published as: DE19719694C2; DE19719694A1

Abstract

The invention relates to a device for detecting and indicating defective vision in at least one eye (75, 76) of a human being (73). A video camera (10) is directed towards said human being (73). The video camera (10) is provided with an arrangement consisting of a diaphragm (14) and light sources (20-23). The recorded image enables defective vision of said human being (73) to be detected. The video image (74) of the human being (73) recorded by the video camera (10) is shown to said human being along with an alphanumeric indication (78, 79) of his or her defective vision.

Description

Device for detecting and displaying a person's ametropia

The invention relates to a device for detecting and displaying the ametropia of at least one eye of a person, comprising:

a) a person-facing video camera comprising: a lens that is substantially half covered by a substantially semicircular aperture;

a plurality of light sources arranged in front of the diaphragm;

Means for measuring the brightness profile of an image of the pupil of the eye recorded by the video camera, along an axis which is substantially perpendicular to the diameter delimiting the diaphragm;

Means for detecting the slope of the brightness curve; and

Means for determining the ametropia from the slope;

and with

b) a video monitor for displaying the video image recorded by the video camera.

An infrared photoretinoscope is known from US-A-4 834 528. The well-known retinoscope, which is also called photoskiascope, comprises a conventional video camera with a lens. Before the opening of the lens, however, an opaque diaphragm is arranged, which is semicircular and covers one half, preferably the lower half, of the lens opening. Several light sources, preferably light-emitting diodes, are arranged in front of the diaphragm. With this well-known infrared photoskioscope the ametropia and the accommodation of eyes can be determined fully automatically. For this purpose, a patient is placed in front of the video camera at a distance of 1 to 2 m. The patient is instructed to look into the lens of the video camera with the eye to be examined. The LEDs emit infrared light that is not visible to the patient. The infrared light emitted from an eccentric position passes through the lens of the eye to be examined and is reflected behind it by the retina of the eye. Depending on how eccentrically the light-emitting diode is arranged relative to the optical axis of the lens and depending on how defective the eye to be examined is, the light cone reflected by the retina of the eye is more or less captured by the upper, open half of the lens of the video camera. The measured video image then consists of a segment of a circle ("crescent"), the position (top / bottom) or size of which enables a statement to be made as to whether the eye is short-sighted (myopic) or farsighted (hyperopic) and how the refraction, ie ametropia, of the Eye size.

From GB-Z "Journal of Physiology", i, pages 301 to 320, 1993, it is known to expand the function of the photoskiascope described above in such a way that several of the differently eccentrically arranged light sources (infrared diodes) are operated at the same time. Instead of a clearly delineated crescent, an image of the eye to be examined is then obtained with an otherwise unchanged examination setup, in which the brightness changes continuously along a vertical axis within the pupil. In the described method, the brightness is measured along this axis, which shows that the brightness curve is linear. The amount and the sign The slope is in turn a measure of the type and strength of the ametropia. In this way, the refraction of the examined eye can be indicated directly and quantitatively (in diopters) by means of suitable calibration curves.

As already mentioned, the known arrangements can be used in the context of medical examinations by an ophthalmologist. The patient has an exclusively passive role in these measurements.

On the other hand, it is known that in a not insignificant proportion of the population there is ametropia of the eyes without these people knowing about it, let alone knowing to what extent the ametropia is developed. This is especially true for children who are naturally less able to articulate and who, due to their limited life experience, are sometimes not even able to subjectively recognize that their vision is reduced.

Series examinations of a large number of people to determine their ametropia only exist to a limited extent, for example in connection with the acquisition of a driving license. In this screening, the subjects are, however, only be required to recognize certain images in a _t double-microscope-like arrangement. It is known that the recognition of these images can be practiced beforehand or the image statement can also be learned by heart. The significance of these studies is therefore limited.

The invention is based on the object of developing a device of the type mentioned in such a way that it is suitable for screening, wherein the patient or test person should have an independent and responsible role.

This object is achieved according to the invention by a device of the type mentioned at the outset, which is characterized by a display unit structurally connected to the video monitor for displaying a value of the determined ametropia, the video camera with the video monitor and the display unit being at a first predetermined location and the person are located at a second predetermined location, and further the video camera with the video monitor and the display unit are positioned and set so that the video image and the display unit can be viewed by the person together and the video image represents at least the face of the person.

The object underlying the invention is completely achieved in this way.

In the device according to the invention, the subject's or person's attention is drawn to the video camera by the fact that the video camera also reproduces a normal video image of the person, as is already known today in sales promotion, for example in shop window displays. However, as soon as the person looks into the video camera of the device, the ametropia of the person (if there is one) can be measured and displayed to the person in the manner described above. It is obvious that serial examinations are possible without any problems, whereby the person concerned is free to draw his or her own conclusions from the displayed values of the ametropia, for example to see an ophthalmologist or an optician. Of particular importance is the moderate device in this context for the detection of ametropia in children. Since children are naturally curious, they will look into the video camera in a special way because they see their own picture on the video monitor next to it. If the data about a possible ametropia of the respective child is then clearly displayed, an adult accompanying the child can take note of these values and take the necessary measures.

In a particularly preferred embodiment of the invention, the light sources are infrared diodes.

This measure has the advantage that the ametropia can be measured at a sufficiently high light intensity without the test person being aware of it, since the infrared radiation is in the invisible spectrum of the light.

It is further preferred if the ametropia is displayed alphanumerically.

This can be achieved either by a large, eye-catching display or by showing the corresponding data in the video image of the person. In addition, numerous other types of representation are also possible, for example graphical representations or the like. , depending on how appropriate, to attract the attention of the person.

In a particularly preferred embodiment of the device according to the invention, the video camera with the video monitor and the display unit are arranged in the display of a shop window and the person is in front of the shop window. This installation of the device has the advantage that, based on known methods of the advertising industry, a real screening is possible in that passers-by passing a retail store are more or less automatically examined for their ametropia and are immediately informed of this fact quantitatively. It goes without saying that this type of presentation is particularly suitable for shop windows of opticians.

Further advantages result from the description and the attached drawing.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination but also in other combinations or on their own without departing from the scope of the present invention.

An embodiment of the invention is shown in the drawing and is explained in more detail in the following description. Show it:

Figure 1 is a front view of a video camera as used in the present invention.

Fig. 2 to 4 schematic optical paths to explain the measurement method underlying the invention;

Fig. 5 to 10 schematic video images of an eye, as it is examined according to the method variants illustrated in FIGS. 2 to 4; 11 shows, on an enlarged scale, a video image of an eye which is examined in accordance with a variant of the methods illustrated in FIGS. 2 to 4;

FIG. 12 shows a brightness curve from the video image according to FIG. 11;

13 shows a characteristic curve determined from the family of curves according to FIG. 12; and

Fig. 14 is an extremely schematic perspective view of an embodiment of a device according to the invention.

In FIG. 1, 10 denotes an otherwise common video camera with a housing 11 and a lens 12 placed on the front. Of a lens 13 of the lens 12, only the upper half can be seen in FIG. 1, since the lower half is by means of a semicircular diaphragm 14 is covered. The diaphragm 14 is delimited on its upper side along a diameter 15 which runs through the center of the objective 12.

In front of the diaphragm 14 there are several rows 20, 21, 22, 23 of light emitting diodes which emit light in the infrared range.

A first row 20 is spaced from the diameter 15 by an eccentricity amount e ₁ , the remaining rows 21, 22 and 23 are each with increasing eccentricity e ₂ , e. or e ₄ arranged. The number of light-emitting diodes in the rows 20 to 23 increases with the eccentricity e _r to e ₄ in order to compensate for non-linearities due to the eccentric arrangement. 2 to 4, beam paths for various measuring arrangements within ophthalmology are shown schematically.

The video camera 10, whose optical axis is designated by 26, can be seen in the right half. An eye 30 is located in the extension of the optical axis 26. A lens 31 and a retina 32 are indicated schematically in the eye 30. The focal plane of the eye 30 is designated 33.

2, if only the first row 20 of light-emitting diodes is switched on, it emits a first light beam 34, which falls through the lens 31 onto the retina 32. Since FIG. 2 is intended to represent the case of nearsightedness (myopia), there is no focusing on the retina 32. Rather, a diffuse image is reflected by the retina 32, as represented by second light beams 35a and 35b. These light beams 35a, 35b intersect in the focal plane of the eye 33 and generate a light cone 36 directed towards the objective 12.

Because of the degree of eccentricity e _{l of} the first row 20 of light-emitting diodes on the one hand and the extent of the nearsightedness of the eye 30 on the other hand, the light cone 36 is designed in a predetermined manner with regard to the angle of inclination and the opening angle. In the case shown in FIG. 2, only a part of the light cone 36, namely the upper half 37 schematically indicated there, passes the aperture on the lens 13 of the lens 12 of the camera 10. This upper half 37 is an image of the lower half 38 of the pupil 39, as shown in FIG. 5, where the video image recorded in FIG. 2 is shown. 5 that the camera 10 records a video image of the pupil 39, in which the lower half of the pupil 39 appears bright, as indicated at 38 with a "crescent", ie a segment of a circle.

3 instead of the first row 20 of light-emitting diodes, e.g. the fourth row 23 is switched on, so there is a slightly modified beam path, in which the light cone 36a is tilted downwards from the situation in FIG. 2, so that the entire light cone 3βa falls within the area of the diaphragm 14.

The associated Fig. 7 shows that the camera 10 therefore takes a ^V ideo image of the pupil 39, which is completely unlit.

At intermediate values of the eccentricity e, correspondingly smaller "crescents" appear, as illustrated in FIG. 6.

4 shows the case of a farsighted ⁽ hyperopic) eye. In this case, the light beams only cross behind the retina 32, so that a light cone 36b is produced, as is shown in FIG. 4. In contrast to the short-sighted eye according to FIGS. 2 and 3, the upper half 37b of the light cone 36b, which falls on the objective 12, thus also depicts the upper half 38b of the pupil. This can be clearly seen in FIG. 8, where the case is shown that only the first row 20 of light-emitting diodes is switched on. 9 and 10 show, analogously to FIGS. 6 and 7, the situations in which the eccentricity e of the rows 20 to 23 increases. If instead of just a single row 20 to 23 of light-emitting diodes all light-emitting diodes are switched on at the same time, an image with continuously varying brightness is formed on the pupil 39, as is illustrated by means of a video image 50 in FIG. 11. The pupil 39 of the eye 30 has a continuously varying brightness curve in the video image 50, in which a lower region 51 of the pupil 39 is bright and an upper region 52 of the pupil 39 is darker. The transition is continuous.

If one now wants to quantitatively measure the brightness curve of the pupil 39, a coordinate system yx 'is placed over the pupil 39. The ordinate y then runs essentially at right angles to the diameter 15 of the diaphragm 14. The abscissa x' is in the case of FIG. 11 placed at the bottom of the pupil 39.

12 shows a family of curves 55 of curves 56 to 58, in which the brightness H is shown as a function of the coordinate axis y. Curve 56 corresponds approximately to the profile of brightness H in video image 50 from FIG. 11, since brightness H decreases with increasing ordinate direction y. This corresponds to a positive refraction, as indicated by positive diopter values + D in FIG. 12.

The second curve 57 relates to an essentially normal-sighted eye, while the third curve 58 represents the case of a far-sighted eye with negative refraction (-D). The slope angle of the approximately straight curves 56 to 58 is designated by α.

13 shows a straight line 60 as a characteristic curve. The straight line 60 represents the linear dependence of the refraction R (measured in Diopter D) of the slope tan α. As illustrated by a point 61 on the straight line 60, for example, a slope of 0.3 corresponds to a refraction of 3 diopters. This means that the brightness curve H (y) can be determined with a measurement according to FIG. 11 and the refraction R in diopter D can be determined directly from the slope of the brightness curve via the characteristic curve according to FIG. 13.

In the device 70 according to the invention, shown extremely schematically in FIG. 14, a video monitor 71 is provided on which a computing and display unit 72 is located. The video camera 10 explained in detail above is arranged on the unit 72.

The video camera 10 is aimed at a person 73, who thus appears in the video image 74 on the monitor 71.

The arrangement is selected and adjusted so that at least the face of person 73 is shown on video image 74. The camera 10 and the monitor 71 are also aligned so that both can be viewed directly by the person 73.

Since the person 73 sees himself on the video image 74, he will turn his attention to the video image 74 and thus also to the camera 10.

The video image 74 shows, among other things, the right eye 75 and the left eye 76 of the person 73.

In the manner described above, the ametropia of person 73 can now be determined, for example, in computing and display unit 72 using the described method. The Defective vision can now be displayed in diopters. This is done, for example, by means of two alphanumeric displays 78, 79, which are located on the front of the computing and display unit 72 directly above the video image 74. Suitable symbols indicate that the values displayed are the ametropia of the right (R) and left (L) eyes. Of course, the values can also be superimposed on the video image 74, or other representations are also possible, for example in graphic form or the like. It is only important that the representation of the values of the ametropia is assigned directly to the video image 74, so that the person 73 recognizes these values immediately and assigns them.

If the device 70 e.g. is arranged in a shop window, for example a shop of an optician, the persons 73, since they look into the display of a shop window of an optician, will in any case establish a certain relationship to their own eyesight and therefore also expect that a corresponding measurement is taken and is shown. A corresponding note ext on the monitor 71 or the unit 72 (not shown) can be helpful here.

Claims

claims

1. Device for detecting and displaying ametropia in at least one eye (30; 75, 76) of a person (73), with:

a) a video camera (10) directed at the person (73), which comprises:

a lens (12) which is substantially half covered by means of a substantially semicircular diaphragm (14);

a plurality of light sources (20 to 23) arranged in front of the diaphragm (14);

Means for measuring the brightness curve (56 to 58) of an image (50) of the pupil (39) of the eye (30; 75, 76) recorded by the video camera (10), along an axis (y) which is essentially on the Diaphragm (14) delimiting diameter (15) is perpendicular;

Means for detecting the slope (tan α) of the brightness curve (56 to 58); and

Means for determining the ametropia from the slope (tan α);

and with b ⁾ a video monitor (71) for displaying the video image (74) recorded by the video camera (10),

characterized by a display unit (72) structurally connected to the video monitor (71) for displaying a value of the determined ametropia, the video camera (10) with the video monitor (71) and the display unit (72) at a first predetermined location and the person (73) are located at a second predetermined location, and further the video camera (10) with the video monitor (71) and the display unit (72) are positioned and set so that the video image (74) and the display unit (72) together from the Person (73) are visible and the video image (74) represents at least the face of the person (73).

2. Device according to claim 1, characterized in that the light sources (20 to 23) are infrared diodes.

3. Apparatus according to claim 1 or 2, characterized in that the ametropia is displayed alphanumerically.

4. The device according to one or more of claims 1 to 3, characterized in that the video camera (10) with the video monitor (71) and the display unit (72) are arranged in the display of a shop window and that the person (73) in front of the shop window.