WO1992004859A1

WO1992004859A1 - Procedure and apparatus for the detection and recording of eye defects

Info

Publication number: WO1992004859A1
Application number: PCT/FI1991/000282
Authority: WO
Inventors: Kari Kaakinen
Original assignee: Kari Kaakinen
Priority date: 1990-09-19
Filing date: 1991-09-17
Publication date: 1992-04-02
Also published as: FI904619A0; AU8502291A; FI904619A

Abstract

The invention concerns a procedure and an apparatus for the detection and recording of eye defects by means of eye photography, in which at least two radiation sources (5, 6) illumining the eye (3) are placed at a distance from the common axis (4) of the eye and the objective in at least two planes passing via said axis, said radiation sources being used simultaneously when the eye is being photographed. According to the invention, at least two radiations of different wavelengths are used in the photographing of the eye.

Description

PROCEDURE AND APPARATUS FOR THE DETECTION AND RECORDING OF EYE DEFECTS

The present invention relates to a procedure as defined in the introductory part of claim 1 and an appara¬ tus as defined in the introductory part of claim 6, designed for use in static skiascopy for the detection and recording of eye defects via eye photography.

Previously known techniques in the art are represent- ed by patent publication US 4 523 820, Kari Kaakinen. The procedure described in this publication is based on a solution whereby the eye, i.e. the cornea and the retina, are photographed simultaneously in at least two meridians of the eye. The procedure can be realized by illumining the eye in the direction of at least two meridians while the eye is being photographed through the objective. In this case, the eye is illumined from at least two points located eccentrically relative to the objective in differ¬ ent meridians. The procedure can also be realized by photgraphing the eye simultaneously from the direction of two meridians relative to the lighting point used for illumination. In this case, the eye is photographed through objectives placed eccentrically relative to this lighting point used for illumination and in different meridians relative to the lighting point. In the case of one lighting point and two objectives placed eccentrically relative to this point, two pictures of the eye under examination are obtained. In the case of one objective and two lighting points placed eccentrically relative to it, only one picture is obtained.

In this known procedure, the eccentric illumination of the eye relative to the objective produces a retina reflection, a so-called red reflection, in which, among other things, possible errors of refraction and changes in the refracting medium of the eye, e.g. cataract opacities etc., are manifested.

In other words, the basic principle of the procedure is that, by illumining the eye simultaneously from at least two points located eccentrically relative to the objective, the eye is photographed simultaneously and in one picture in two different meridians. In this case, the light proceeding from two different points and the dif¬ fused light do not essentially disturb or confuse the observations, but instead the changes of refraction appear simultaneously from at least two meridians. The changes of refraction may also appear from both meridians in a partially or largely overlapping manner, which, however, is not always a serious impediment to their observation, although it does cause a certain degree of inaccuracy and involves the possibility of error especially when the changes of refraction are mainly overlapping in the picture obtained. The procedure has a decisive importance in the detection and recording of eye defects and in the screening of defects. Before the introduction of this procedure, the patient had to undergo a personal dia^¬ gnostic examination, which was very difficult, laborious and even impossible in the case of small children. Now, corresponding examinations can be carried out by photo- graphing the patients' eyes and performing the screening and more detailed examination of the results on the basis of the photographs.

The object of the present invention is to provide improvements to the procedure described above. In particu- lar, the object of the invention is to provide a procedure that allows more accurate and varied detection and record¬ ing of eye defects than has been possible so far. Thus, the object of the invention is to enable the changes of refraction to be recorded upon each other in the same picture in such a way that the two or more overlapping pictures obtained in different meridians of the eye do not cover each other so as to give rise to incaccuracies or errors in their interpretation due to the overlapping. As for the features characteristic of the invention, reference is made to the claims.

The invention concerns a procedure for the detection and recording of eye defects by means of eye photography. In this procedure, the eye is illumined during the photo- graphing by using simultaneously at least two radiation sources placed at a distance from the common axis of the eye and the objective in at least two planes passing via said axis. According to the invention, the radiation sources used simultaneously emit radiations of at least two different wavelengths in different meridians of the eye, so that the radiations are reflected differently, e.g. in different colours, from essentially the same eye structures. In this manner, more accurate and more varied information is obtained about the eye than has been possible to obtain by previously known methods.

The radiation used may consist of certain wavelength bands of visible light of different colours, suitable IR radiation, UV radiation or laser radiation. Also any other kinds of radiation with which the eye can be irradiated without damaging it and which are reflected back from the

In an embodiment of the invention, although the procedure uses two or more different radiations at the same time, the reflected different radiations are received in the same recording device, by means of which only one picture of the eye is produced. Since the reflected radiations are of different colours, they can be relative¬ ly easily observed and examined in a single picture with overlapping images. In this way, a single picture provides accurate information about the eye in two or more eye meridians. On the basis of the picture, it is possible e.g. to directly calculate the strengths of the lenses required by the eye, which would not be possible with sufficient accuracy unless the overlapping pictures were distinguished from each other.

It is also possible, e.g. by using suitable filters and reflectors, to direct each of the different radiations reflected from the eye into separate suitable recording devices, thus producing as many different pictures taken simultaneously of the eye as there are different radiation sources in use.

The essential point in the procedure of the invention is that, although different pictures are taken in two or more eye meridians, they are all taken essentially simul¬ taneously and thus the photographic conditions are identi¬ cal in all pictures and the images are completely compara¬ ble with regard to each other regardless of whether they are presented in the same picture as superposed images in different colours or as separate pictures. In this way, e.g. errors of refraction in different meridians of the eye can be detected and recorded from the pictures pre¬ cisely and accurately. The apparatus of the invention for the detection and recording of eye defects comprises a camera together with its objective and at least two radiation sources placed at a distance from the common axis of the eye and the objec¬ tive in at least two planes, meridians, passing via said axis, said sources being used simultaneously to illumine the eye. According to the invention, the radiation sources differ from each other so that the radiations emitted from them into the eye are different, which means that they are refracted differently in different strata of the eye and thus give different reflections from the eye. In this way, radiations of different colours or wavelengths describe different meridians of the eye in the measurement of the error of refraction. As may be known, the refractive power is measured in the meridian passing via the centre of the objective and the light source.

In a preferred embodiment of the invention, two or more of the radiation sources used are identical except that they are provided with suitable filters placed in front of them, which permit only certain wavelengths or ranges of wavelengths differing from each other to pass through into the eye.

Similarly, it is naturally possible to use only one radiation source together with e.g. suitable optics to divide the radiation into several beams meeting the eye in different meridians, these beams being then treated with suitable filters.

In an embodiment of the apparatus, the apparatus comprises several light sources which are placed at different distances from the centre of the lens and emit different wavelengths, and which may flash at different times, in which case the degree of eccentricity and the refracting meridian will be known in the recording pro¬ cess. As compared to previously known techniques, the invention provides the advantage that it allows more accurate and more varied information to be obtained about eye defects.

In the following, the invention is described in detail by referring to the appended drawings, in which

Fig. 1 presents a diagram representing an arrangement as provided by the invention.

Fig. 2 presents another arrangement of the invention, and Fig. 3 presents images obtained by previously known techniques and by the procedure of the invention.

The diagrammatic arrangement of the invention illus¬ trated in Fig. 1 comprises a camera 1 together with its objective 2 and the eye 3 under examination, which is located at a dist •_ance of the order of e.g. 1 m from the camera on the same optical axis 4 with the objective 2. Arranged at a distance from the axis 4 in two different planes passing via the axis 4 are two radiation sources 5 and 6. In this embodiment, these radiation sources are identical and are therefore provided with suitable differ¬ ent filters 7 and 8, so that the radiations falling on the eye from the radiation sources 5 and 6 are different, having different wavelengths or wavelength ranges. There¬ fore, in addition to meeting the eye from different angles and thus providing different information about the eye, the radiations also convey different information about the eye to the camera because of the differences in wave¬ length.

Naturally it is possible to use radiation sources 5 and 6 that are different in themselves, i.e. emit radia¬ tions differing in themselves without the need for filters between the eye 3 and the radiation sources. The radiation sources may be known devices emitting visible light or IR, UV or laser radiation. Fig. 2 presents, in front view relative to the camera 1 and the objective 2, an arrangement according to the invention in which three radiation sources 5 are placed around the optical axis 4 at even distances of 120° from each other and at a distance from the axis, each radiation source emitting a different kind of radiation to the eye and thus producing reflections that provide different information about the eye to the camera.

Figures 3A and 3B present eye reflections obtained by previously known photographic techniques. In both figures, the eye has been photographed in two meridians of the eye with the same lighting. The segments representing the refractive power of the eye thus obtained are partly overlapping. Since in practice the lines representing the chords of the segments are not clear and sharp but steple- ssly fading, vague, it is often difficult to interpret partially overlapping images of the same colour and the interpretation is inaccurate. Especially in Fig. 3B, where the segments cover more than one half of the circle, it is difficult to determine the segment height with sufficient accuracy.

Figures 3C and 3D present corresponding pictures obtained by the procedure of the invention. Since pictures taken in different meridians are different, of different colours, when recorded on film, the overlapping of the images presents no obstacle to the interpretation of individual images, and the segment heights x and y can be easily measured from the pictures with sufficient accuracy regardless of the magnitudes or overlapping of the seg- ments. According to the invention, by using different radiations, e.g. different colours, the eye can also be photographed in more than two meridians simultaneously, in which case the information obtained about the eye is still more accurate. In the foregoing, the invention has been described by presenting examples with reference to the drawings at¬ tached, but different embodiments are possible within the scope of the idea of the invention as defined in the claims.

Claims

1. Procedure for the detection and recording of eye defects by means of eye photography, in which procedure at least two radiation sources illumining the eye are placed at a distance from the common axis of the eye and the objective in at least two planes passing via said axis, said radiation sources being used simultaneously when the eye is being photographed, c h a r a c t e r i z e d in that at least two radiations of different wavelengths are used in the photographing.

2. Procedure according to claim 1, c h a r a c t e ¬ r i z e d in that the photographing is performed using simultaneously radiations which are reflected in different colours out of the eye, each radiation providing different information about the eye.

3. Procedure according to claim 2, c h a r a c t e ¬ r i z e d in that the reflections of different colours are recorded as overlapping images on the same film.

4. Procedure according to claim 2, c h a r ¬ a c t e r i z e d in that the reflections of different colours are filtered so as to separate them from each other and recorded on the film as separate pictures.

5. Procedure according to claim 1, c h a r - a c t e r i z e d in that the radiation used consists of different wavelength bands of visible light, or of IR radiation, UV radiation and/or laser radiation.

6. Apparatus for the detection and recording of eye defects by means of eye photography, comprising a camera (1) together with its objective (2) and at least two radiation sources (5,6) placed at a distance from the common axis (4) of the eye (3) and the objective in at least two planes passing via said axis, said sources being used simultaneously to illumine the eye, c h a r a c t e r i z e d in that the first radiation source (5) emits a radiation of a certain wavelength while the second radiation source (6) emits a radiation of another given wavelength differing from that of the first radiation source.

7. Apparatus according to claim 6, c h a r ¬ a c t e r i z e d in that the radiation source (5,6) is a device emitting visible light, IR, UV and/or laser radiation.

8. Apparatus according to claim 6 or 7, c h a r a c t e r i z e d in that the radiation source emitting a radiation of a certain wavelength consists of a lamp, e.g. a flash light, and a filter placed in front of it.

9. Procedure according to any one of claims 6-8, c h a r a c t e r i z e d in that the objective (2) of the camera (1) is located at a distance from the eye (3), the distance being 0.1 - 5m, preferably 0.5 - 2m, e.g. approx. lm.

10. Procedure according to any one of claims 6-9, c h a r a c t e r i z e d in that the apparatus comprises several light sources which may be placed at different distances from the centre of the lens and which emit different wavelengths.