GB2220084A - Ophthalmoscopic device - Google Patents

Abstract

An adaptor or attachment for a direct ophthalmoscope comprises a housing (22) having sight holes (25) in use aligned with a sight hole (14) in the ophthalmoscope (12) and with a reflector arrangement (15 and 18) to intercept about half of the light from the ophthalmoscope's sight hole and deflecting it to the user's second eye. An afocal optical system (16 and 17) can be disposed between the reflectors. The device can be adapted for use by a one-eyed user by deflecting all the light from the ophthalmoscopes sight hole.

Description

OPHTHAIMOSCOPIC DEVICE FIELD OF THE INVENTION The present invention concerns an ophthalmoscopic device in the form of an adapter or attachment which can be integral with an ophthalmoscope or used as an accessory to convert a direct ophthalmoscope to binocular use or to offset the viewing point from the main axis of the ophthalmoscope.

BACKGROUND OF THE INVENTION Ophthalmoscopes are well known and are discussed in standard works such as Bennett and Rabbetts "Clinical Visual Optics? published by Butterworths in 1984.

There are two main types of ophthalmoscopes. One- in which the patient's eye is viewed as through a magnifying glass is called a direct ophthalmoscope; it is to be remarked that the patient's eye and the eye of the user each contain a lens. The other main type is the indirect ophthalmoscope in which a positive lens is used to project an image of the patient's eye and it is this image which is examined by the user. The indirect ophthalmoscope can be converted to binocular use by means of a beam splitter. The direct ophthalmoscope is generally more useful and only when the special advantages of the indirect type are required is the indirect type used.

In use the direct type is very close to the patient's eye and it is preferred to use the user's right eye to examine the patient's right eye and the user's left for the patients left. This is of course difficult when the user has not got good vision in one of his own eyes. The present invention aims at adapting a direct ophthalmoscope for greater versatility.

SUMMARY OF THE PRESENT INVENTION The present invention in one of its aspects provides an adapter or attachment for a direct ophthalmoscope comprising a housing for attachment to the ophthalmoscope, the housing fitting around the sight hole of the ophthalmoscope, a reflector in the housing disposed to intercept at least part of a beam passing through the sight hole and to deflect it transversely or substantially so, a second reflector for restoring the direction of travel of the deflected beam to be substantially parallel to the undeflected beam, and a sight hole for at least the beam fron the second reflector.

The adapter or attachment for a user with only one good eye can be arranged to deflect all of the beam passing through the sight hole and have only a single eye piece offset from the main axis of the ophthalmoscope.

This might also be usefu' in general use since patients often feel that the user is trying to climb into them and jest that there is no room for the user in the patient's eye but with an offset ophthalmoscope the user need not have his face so unpleasantly close to the patient.

However for more general use only roughly half of the beam would be deflected with the undeflected beam passing straight to one eyepiece and the deflected beam going to another eyepiece so giving binocular vision provided that the intercepted half beam is that half nearer the deflected beam. In indirect ophthalmoscopes adapted to give binocular vision as for example shown in U. S Patent 4 015 898 the main beam is split into equal parts which are each deflected transversely (in opposite directions) and then viewed through interchangeable binocular or magnifying binocular units. This ensures that the light paths are of equal length. In the present invention, the longer light path uses substantially collimated light and the light path is effectively shortened by the use of an afocal optical system.

A second aspect of the invention provides an attachment for use as an accessory for a direct ophthalmoscope comprising a housing adapted to be easily attached to, and removed from, the ophthalmoscope, the housing containing a first reflector disposed to intercept at least part of the light entering the housing through the ophthalmoscope's sight hole and to deflect it through substantially ninety degrees to a second reflector which restores the direction of travel of the light.

Another aspect of the present invention provides an attachment for use as an accessory for a direct ophthalmo scope comprising a housing adapted to be easily attached to, and removed from, the ophthalmoscope, the housing containing a a first reflector disposed to intercept part of the light entering the housing through the ophthalmoscope's sight hole and to deflect that light through substantially ninety degrees to a second reflector which restores the direction of the light so it can be viewed by a user 5 second eye, the first eye viewing the unintercepted light, and the housing containing the second reflector which is adjustable in position to adjust the attachment to the user's eye spacing.

Ghe reflectors can be in the form of mirrors or prisms and it may be possible to use bundles of optic fibres which would serve the role of reflectors to deflect the light.

The adaptor or attachment is preferably mounted on the ophthalmoscope so it can be swung around the sight hole and so the adaptor, or attachment,can be to the left or right of the ophthalmoscope with preferably a parking position in line with the ophthalmoscope.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view showing the optical arrangement of the device according to the present invention, Figure 2 is an exploded perspective view with a housing part-broken-away, Figure 3 and Figure 4 show enlarged details of alternative ways of attaching the device to an ophthalmoscope with co-operating faces opened out, and Figure 5 illustrates an ophthalmoscope fitted with the device.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT Figure 1 shows the optical arrangement of an adapter or attachment according to the present invention. A patient's eye 11 is being examined by a direct ophthalmoscope 12 which in the normal way directs a beam of light into the eye 11 and receives a reflected beam which is viewed by a user's eye 13 through a sight hole 14 in the ophthalmoscope. The adapter or attachment comprises a housing (not shown in Figure 1) attached to the ophthalmoscope around the sight hole containing a first reflector 15 for deflecting half the beam of light through the sight hole transversely, two lenses 16 and 17 forming an afocal lens system for the deflected beam,and a second reflector 18 for restoring the direction of the deflected half beam to be parallel the undeflected half beam.The second reflector conveniently consists of two prisms 19 and 20 with prism 19 arranged to return the half beam along a parallel path offset to its preprism path onto the second prism which directs the half beam in the desired final direction wherein it can be viewed by the cs Jith his other eye 21. The prisms 19 and 20 are preferably arranged so that the prism 19 is about twice as far from the lens 17 an the prism 20 and can be made adjustable within the housing to vary the position of the final half beam to suit the spacing between the eyes of the user. Conveniently the adjustable locating means (not shown in Figure 1) maintains the prism 20 halfway between the lens 17 and the prism 19. The lenses 16 and 17 can be full lenses as shown in broken line or can be part lenses consisting only of the parts of the full lenses actually used, and can in fact be cut from full lenses. A field lens 9 can be located between the lenses 16 and 17 if desired. Whilst theoretically it is desirable to have the prism 20 half-way between the lens 17 and the prism 19, in practice this does not seem to be crucial or even significant.

It is not essential to maintain the prism 20 halfway between the prism 19 and the lens 17 and Figure 2 shows,in exploded perspective view with a part broken away,a suitable mechanical arrangement. A light compact narrow unobtrusive housing 22 is formed by a base plate 23 and a lid 24. The base plate has sight holes 25 in use in line with the sight hole of the ophthalmoscope and carries the first reflector 15 and the lenses 16 and 17. Slidable in the housing under the control of a positioning screw 26 is a stirrup 27 carrying the prisms 19 and 20 which as shon are bonded together by an optically clear cement.If it is desired to maintain the desired positioning of the prisms in relation to the lens 17, the prism 20 could be located for sliding motion in its correct orientation and mounted for driving by a lever fixedly pivotted at one end and pivotted to the stirrup at its other end and engaging the prism by a pinand-slot mechanism. The light from the prism 20 is directed through a second sight hole in the form of a a slot 28.

The housing 22 can be attached to the ophthalmoscope 12 as shown in Figure 3 or 4. In Figure 3 a mounting plate 29 is secured by glue, straps or otherwise to the ophthalmoscope 12. This mounting plate has a central sight hole 30 and a plurality of mushroom shaped projections 31 such as flat-headed screws disposed on a pitch circle around the sight hole. By having the sight hole slightly larger than the sight hole in the ophthalmoscope it is possible to position the mounting plate accurately.The housing 22 is provided with keyhole shaped slots 32 so the projections can be engaged and locked in the slots in a number of orientations such that the housing projects from the right or left of the ophthalmoscope; it may be desirable to be able to park the attachment or adapter in an inoperative position say in line with the ophthalmoscope and with four projections this is easily achieved and if the sight hole 30 is displaced slightly down the ophthalmoscope the first reflector will not intercept any of the light. Figure 4 shows a very similar arrangement except that the housing is secured to the ophthalmoscope by magnetic attraction with a magnetic mounting plate 34 and co-operating magnetic provisions in the housing. The plate 34 can be provided with a domed projection 35 which can engage in recesses 36 in the housing which can be recessed at 37 receive the entire plate 34. Instead of one domed projection there can be a number of such projections positioned to fit into the recesses 36 or a suitable magnetic arrangement could be used to provide both attachment and indexing (the accuracy of indexing is not crucial). It would be possible to have the mounting plates 29 and 34 integral with the ophthalmoscope. For example, the projections 31 can be in the form of screws directly attached to the ophthalmoscope. It would be possible to have the housing permanently and rotationally captive on the ophthalmoscope.

Figure 5 shows the ophthalmoscope fitted with an adaptor or attachment.

Claims (14)

C L A I M S

1. An adaptor or attachment for a direct ophthalmoscope comprising a housing for attachment to the ophthalmoscope, the housing-fitting around the sight hole of the ophthalmoscope, a reflector in the housing disposed to intercept at least part of the beam passing through the sight hole and to deflect it transversely or substantially so, a second reflector for restoring the direction of travel of the deflected beam to be substantially parallel to the undeflected beam, and a sight hole for at least the beam from the second reflector.

2. An adaptor or attachment according to claim 1 wherein the first-mentioned reflector is arranged to intercept substantially half of the beam from the ophthalmoscope's sight hole with the remainder passing to a sight hole, and wherein the second reflector is displaceably mounted in the housing so as to adjust the final travel of the deflected beam to suit a user's eye spacing, the sight hole associated with the second reflector being in the form of a slot.

3. An attachment for use as an accessory for a direct ophthalmoscope comprising a housing adapted to be easily attached to, and removed from, the ophthalmoscope, the housing containing a first reflector disposed to intercept at least part of the light entering the housing through the ophthalmoscope's sight hole and to deflect it through substantially ninety degrees to a second reflector which restores the direction of travel of the light.

4. An attachment for use as an accessory for a direct ophthalmoscope comprising a housing adapted to be easily attached to, and removed from, the ophthalmoscope, the housing containing a first reflector disposed to intercept part of the light entering the housing through the ophthalmoscope's sight hole and to deflect that light through substantially ninety degrees to a second reflector which restores the direction of the light so it can be viewed by a user's second eye, the first eye viewing the unintercepted light, and the housing containing the second reflector which is adjustable in position to adjust the attachment to the user's eye spacing.

An attachment according to claim 3 or chair L further comprising an adaptor plate for permanent attachment to the ophthalmoscope, the housing and the plate ain complementary means for securing the housing and the plate toether.

6. An attachment according to claim 5 wherein the complementary means include indexing means enabling the housing to be located angularly relative to the ophthalmoscope.

7. An attachment according to claim 5 or claim 6 wherein the complementary means includes magnetic elements to hold the housing to the plate.

8. An adaptor or attachment according to any one of the preceding claims having between the two reflector means an afocal optical system, and the second reflector is designed to correct for any image inversion caused by the afocal optical system.

9. Im adaptor or attachment according to claim 8 wherein the afocal optical system comprises lenses.

10.An adaptor or attachment according to claim 9 wherein the lenses are segmental lenses.

11.An adaptor or attachment according to claim 9 or 10 wherein a field lens is disposed in the afocal optical system.

12.An adaptor or attachment according to any one of the preceding claims wherein the housing is arranged to be positioned angularly with respect to the ophthalmoscope and to be rotated about the ophthalmoscope s sight hole.

13. An adaptor or attachment substantially as herein described with reference to Figures I and 2 of the accompanying drawings.

14. An adaptor or attachment according to claim 1;; with the means as illustrated in Figure 3 or Figure 4 of the acco#-panying drawings.