WO2005044097A2

WO2005044097A2 - Ophthalmoscope

Info

Publication number: WO2005044097A2
Application number: PCT/GB2004/004433
Authority: WO
Inventors: Roger Hanif Armour
Original assignee: Ophthalmos Limited
Priority date: 2003-10-21
Filing date: 2004-10-20
Publication date: 2005-05-19
Also published as: GB0324526D0; GB0423316D0; GB2407395A; AR046550A1; GB2407395B; WO2005044097A3

Abstract

An ophthalmoscope comprising (1): means (3) arranged to direct light along a path (B) exiting the ophthalmoscope (1) through a first aperture (4) and into a subject eye; a second aperture (5) through which an user can view a subject eye along a sight path (D) extending generally parallel to the exiting light path (B) ; and means (3) partially eclipsing (20) the sight path along which an user can view a subject eye. A baffle (8) may be provided between a light source and the light directing means (3) and/or the first, aperture (4) , to enhance definition of the image of the subject eye.

Description

Ophthal oscope

Field of the Invention

This invention relates to an ophthalmoscope and especially, but not exclusively, to an ophthalmoscope which is simple and inexpensive to manufacture.

Background to the Invention

An ophthalmoscope is usually a complex optical instrument used for examining the retinae of human and animal eyes. Generally, ophthalmoscopes have more than twenty lenses and from three to six lights and, as such, are intricate and costly to manufacture and buy.

Ophthalmoscopes are used routinely during the day- to-day work of doctors, optometrists, veterinary surgeons, health workers and trainees thereof.

However, due to the expensive nature of this instrument, only limited numbers are available for actual use and certainly there is no way that an ophthalmoscope can be provided for each, for example, doctor, medical student or trie like, who needs to use one .

Due to the shortage of these instruments and their complexity, students and even non-specialised medical staff very often do not get a chance to learn how to use this instrument properly. This situation is worse in less developed and third world countries where in some places there are no ophthalmoscopes available to local doctors or aid workers, because they are simply too expensive to buy or manufacture.

The problem of the restricted numbers of ophthalmoscopes in hospitals, opticians and veterinary surgeries, along with the associated lack of expertise in using the instrument, when available, is therefore potentially serious and any attempt to reduce the complexity of the instrument and the manufacturing costs, is sought.

Any method of producing cheaply a simple ophthalmoscope is therefore sought.

In GB-A-2387663, there is described a lens-free ophthalmoscope which reduces glare in a user' s eye, thereby improving the view of a subject eye through the sight hole and which comprises: means defining a first light path; reflective means arranged to divert light from the first light path along a second light path exiting the ophthalmoscope through a first aperture and into a subject eye; a second aperture through which an user can view a subject eye along a path extending generally parallel to the second light path; and a baffle which is arranged between the first light path and the second aperture. Present Invention

However, it has been found that it is possible to reduce even further glare in an user's eye through the sight hole or second aperture by suitably modifying the above-described ophthalmoscope.

One aspect of the invention provides an ophthalmoscope comprising:

means arranged to direct light along a path exiting the ophthalmoscope through a first aperture and into a subject eye;

a second aperture through which an user can view a subject eye along a sight path extending generally parallel to the exiting light path; and

means partially eclipsing the sight path along which an user can view a subject eye.

Preferably, the ophthalmoscope is lens-free.

Preferably also, the partial eclipsing means is located intermediate the first and second apertures.

The partial eclipsing means may comprise a baffle, in which case, the light directing means, such as a mirror, prism, fibre optic device or any combination thereof, may be associated with the baffle. For example, the light directing means may be mounted on the baffle and can be arranged to divert light on a first path from a light source along a second light path exiting the first aperture and constituting the exiting light path.

In such an arrangement, any such baffle of the partial eclipsing means may enhance the elimination, or at least substantial reduction, of any spurious light from the first light path which might otherwise cause glare at the second aperture. In such an arrangement also, another baffle may be provided along the first light path between the light source and the first aperture .

This other baffle may have a free end which, along a line or plane extending generally parallel to the first light path from a light source, is coincident with, but preferably not overlapping, an extreme end of the diverting light directing means adjacent the sight path but which can project into the first light path from any light source, thereby enhancing the elimination or the substantial reduction of any further glare generated at the second aperture by spurious light from the first light path.

Additionally or alternatively, the light directing means may comprise a light source, such as an LED array, plasma screen or other suitable compact light generator, located intermediate the first and second apertures, which may be associated with any baffle located intermediate those two apertures for directing light directly along the exiting or second light path exiting the first aperture of the ophthalmoscope. Such a light source may be mounted upon the baffle or may be arranged to transmit light directed therethrough along the exiting or second path exiting the first aperture.

Preferably, the generally parallel exiting or second light and sight paths are as close to one another as possible and may have portions thereof which are coincident with each other between the light directing means and first aperture.

Light from a light source may be collimated, with the light source being provided as an integral component of the ophthalmoscope or as a detachably removable component thereof.

Another aspect of the invention resides in an ophthalmoscope comprising:

means in which a first light path is defined;

means arranged to divert light from the first light path along a second light path exiting the ophthalmoscope through a first aperture and into a subject eye; and

a second aperture through which an user can view a subject eye along a sight path extending generally parallel to the second light path, wherein the light diverting means partially eclipses the second aperture on the sight path along which an user can view a subject eye.

Preferably, the ophthalmoscope is substantially lens-free .

A baffle may be arranged between the first light path and the second aperture, whilst another baffle may be arranged between the light source and the light diverting means and/or the first aperture.

In this second aspect of the invention, the ophthalmoscope may also comprise a light source, which can be incorporated with the other components of the ophthalmoscope as an integral component thereof or which may be provided as a separate, detachably removable component of the ophthalmoscope.

In each of the first and second aspects of the invention defined above, the means in which the first light path is defined, may comprise a tube wherein, preferably, at least the wall of the tube is opaque and the inner surface thereof may be non-reflective. The light from any light source may be collimated.

The light diverting means may comprise a mirror, preferably semicircular, which can be inclined at approximately 45° to the first light path and/or the second light path. Alternatively, such means may comprise a prism. Otherwise, the light diverting means may comprise a bent or angled section of a fibre optic, light guide device, in which case, such a device may at least partially constitute the first and/or second light path(s) .

The first aperture can be formed in, for example, any tube in which the first light path is defined. Any such aperture is preferably circular, whilst the second aperture may be in the otherwise closed end of the tube, for example, in an inclined roof of the tube. Again, this second aperture is preferably circular.

The light diverting means, such as a mirror or prism, may be associated with a baffle which is preferably either a flange or a block. With a block, such means is preferably mounted thereon.

A further aspect of the present invention provides an ophthalmoscope comprising:

means in which a first light path is defined;

means arranged to divert light from the first light path along a second light path exiting the ophthalmoscope through a first aperture and into a subject eye; a second aperture through which an user can view a subject eye along a sight path extending generally parallel to the second light path; and

a baffle which is arranged between the light source and the light diverting means and/or the first aperture .

Preferably, the ophthalmoscope is lens-free.

A light source may be incorporated integrally with the other components of the ophthalmoscope or may be in the form of a separate, detachably removable light source .

The baffle may, as indicated, be provided along the first light path between the light source and the first aperture, in which case, that baffle may have a free end which, along a line or plane extending generally parallel to the first light path from any light source, is coincident with, but preferably not overlapping, an extreme end of the light diverting means adjacent the sight path but which could project into the first light path, thereby enhancing the elimination or the substantial reduction of any further glare generated at the second aperture by spurious light from the first light path.

As in the case of the ophthalmoscope described in GB-A-2387663, a baffle may also be provided between the first light path and the second aperture. It has been found that, in the various aspects of the invention defined and described above, the definition of the image of the eye viewed by an user through the second aperture is improved by suitable determination of the positioning and dimensioning of the light directing or diverting means, such that the light directing or diverting means can partially overlap or eclipse the second aperture, whereby at least part of each of the generally parallel sight path, along which a subject eye can be viewed through the second aperture, and the exiting or second light path, as the case may be, can be brought into substantial coincidence with each other.

It has been found that a preferred range of 10% to 50% overlap of the second aperture by the light directing or diverting means provides much improved definition of the images of subject eyes, a more preferred range being 20% to 30% overlap.

Throughout this specification the term "lens-free" is used in relation to an ophthalmoscope which is totally devoid of any lens(es) or which includes a lens of a trivial nature, for example, a collimating lens, not affecting the overall operation and efficiency of the ophthalmoscope.

Thus, it can be seen that an ophthalmoscope in accordance with each aspect of the invention, as defined above, can provide an inexpensive product which is simple to use and prevents, or at least reduces substantially, any glare or other scattered, undesirable light due to the enhanced elimination or at least substantial reduction, of any undesirable light exiting the ophthalmoscope via its second aperture into the eye of a user, as well as enhancing the definition of the image of a subject eye.

Brief Description of the Drawings

Figure 1 is a side elevation of one half of a first embodiment of ophthalmoscope;

Figure 2 is a front elevation of the ophthalmoscope of Figure 1;

Figure 3 is a sectional side elevation of the ophthalmoscope shown in Figures 1 and 2, along the line A-A in Figure 2;

Figure 4 is a section, on an enlarged scale, of the circled portion of the ophthalmoscope;

Figure 5 is a sectional side elevation of a second embodiment of ophthalmoscope; and

Figure 6 is a sectional side elevation of part of a third embodiment of ophthalmoscope.

Referring, therefore, to Figures 1 to 4, a first embodiment of lens-free ophthalmoscope, indicated generally at 1, comprises an opaque upper tube 2 in which is defined a first light path A between the pair of parallel dashed lines, reflective, light diverting means in the form of a planar, semi-circular mirror 3, a sight hole in the form of a first, generally circular aperture 4 in the side wall of the tube 2, an eyepiece in the form of a second aperture 5, again generally circular, in an inclined roof 7 of the tube 2, and a baffle 6 which is in the form of a flange or block located between the first light path A and the second aperture 5 and upon which the mirror 3 is mounted. As can be seen, no lenses are employed.

Collimated light passing along the first light path A from a light source (not shown) incorporated in a lower tube (also not shown) to which the upper tube 2 is or can be hinged at 20, is reflected through 90° at the 45° angled mirror 23 along a second light path B between the parallel chain-dotted lines, which then passes through the first aperture 4 and into a subject eye (not shown) .

The eye of an observing user is able to view the retina of the subject eye along a sight path D extending through the second and first apertures 5, 4, such sight path D being generally parallel to the second light path B and having an edge portion substantially coincident with a corresponding portion of the second light path B. This arrangement is possible, in that the upper portion of the mirror 3 partially eclipses the aperture 5, as at 20, this having been found to enhance the definition of the image of the subject eye viewed by the user along the sight path D.

Because the baffle 6 and mirror 3 are located between the first light path A and the second, eyepiece aperture 5, any spurious light from the first light path A which might otherwise pass through that aperture 5 into the eye of an user, is substantially reduced, thereby reducing glare and enhancing the user' s view of the subject eye 20. Such glare is further reduced by the presence of another baffle 8 located on the inner wall of the tube 2 adjacent the first aperture 4 and between that aperture 4 and the light source.

Other spurious light from the first light path A which is not diverted along the light path B tends to be absorbed by the matt black interior surface of the inner wall of the tube 2.

Turning now to the second' embodiment of ophthalmoscope 11 shown in Figure 5, again only the upper tube 12 in which is defined a first light ^'path A is shown, along with a planar semi-circular mirror 13, a sight hole in the form of a first circular aperture 14 in the side wall of the tube 12, an eyepiece in the form of a second circular aperture 15 in the inclined roof 17 of the tube 12 and a block 16 upon which the mirror 13 is mounted and which, in turn, is mounted to the tube roof 17. Again, no lenses are used. Light from a lower light source (not shown) passing along the first light path A defined in the tube 12, is reflected by the mirror 13 through 90° along the light path B and then into a subject eye (also not shown), via the first aperture 14.

The eye can be viewed by the eye of an observing user along a path D extending through the second and first apertures 15, 14.

The combination of the block 16 and mirror 13, as well as the dimensions thereof, and particularly the thickness, of the block 16, acts as a baffle between the first light path A and the second viewing aperture 15, thereby substantially reducing spurious light, and hence associated glare, from the first light path A which might otherwise enter the user's eye via the second viewing aperture 15.

As in the case of the first embodiment described above in relation to Figures 1 to 4, this second embodiment also enhances the viewing capability of a user's eye 50 into the subject eye along the sight path D, as shown, which is substantially parallel to the secon light path B and partially coincident with that path B .

Definition of the image of the subject eye is also enhanced, due to the partial eclipse of the second aperture 15 by a portion of the mirror 13, as in the case of the first embodiment. A generally annular baffle 18 can also reduce spurious light, and hence further glare, emanating from the light path A and exiting the ophthalmoscope via the second aperture 5.

Figure 6 shows a third embodiment of ophthalmoscope 21, more particularly the upper portion of a tube 22 in which is defined a first light path A. A baffle 26 is located between the first light path A and an eyepiece in the form of a second window 25, with a mirror 23 mounted at the upper edge region of the baffle 26.

Collimated light on the light path A is reflected through 90° at the 45° angled mirror 23 along a second light path B which passes through a sight hole in the form of a first aperture 24 and into a subject eye (not shown) .

An observing user is able to view the subject eye along a sight path D extending through the first and second apertures 24,25, such sight path D being generally parallel to the second light path B and having an edge portion substantially coincident with a corresponding edge portion of the second light path B. In this arrangement, the upper portion of the mirror 23 partially eclipses, at 30, the second aperture 25 and, as discussed above in relation to the first and second embodiments, enhances the definition of the image of the subject eye observed by the user along the sight path D. The eclipsing overlap is preferably 10% to 50% of the height of the second aperture 25 but more preferably 20% to 30% of the height thereof.

Such definition can be further enhanced if, as shown in Figure 6, a further baffle 28 is provided between the light source (not shown) and the first aperture 24, particularly with the inner free end 28' of that baffle 28 being coincident with but not overlapping the tip 23 ' of the mirror 23 along a chain- dotted line (or plane) 30 extending generally parallel to the first light path A.

A similar arrangement could be achieved with the free end of the baffle 8 described above with reference to the first embodiment of Figures 1 to 4.

In Figure 6, the further baffle 28 does, in fact, constitute an internally-threaded eye which is one of a pair of complementary eyes on respective halves of the tube 22, through which a retaining screw is receivable.

Thus, it can be seen that an ophthalmoscope 1,11,21 in accordance with the invention eliminates, or at least substantially reduces, glare in the eye of an observing user, thereby dramatically improving the user's view of a subject eye, whilst also substantially eliminating the use of lenses, thereby reducing manufacturing costs considerably, and enhancing definition of the image of the subject eye viewed by an user. It is to be appreciated that components other than those referenced above may be employed in the ophthalmoscope 1,11,21. For example, the mirror 3,13,23 may be replaced by a suitable prism or by a bent or angled section of fibre optic light guide device or other suitable fibre optic device, in which case, such may also be used to at least partially define the first and/or second light path(s) A,B, whilst, as an option, partially eclipsing the second viewing aperture 5.

Also, it is to be understood that the ophthalmoscope embodiments described above, and indeed any ophthalmoscope falling within the scope of the present invention, can be lens-free, even though an associated light source may be provided with some type of lens arrangement for collimation of the first light path from a light source. Such collimation may be provided by the integral shape of, say, a light bulb, or by a collimating lens associated with the light source but not the ophthalmoscope itself. Thus, any such lens arrangement is not to be considered as part of the actual structure and operation of any lens-free ophthalmoscope in accordance with the invention.

In any event, and as discussed above, the term^Xlens-free", as used throughout this specification, is used in relation to an ophthalmoscope which either is totally devoid of any lens(es) or includes a lens of trivial nature which does not affect the overall operation and efficiency of the ophthalmoscope.

Claims

1. An ophthalmoscope comprising:

2. An ophthalmoscope according to claim 1 which is lens-free .

3. An ophthalmoscope according to claim 1 or 2, wherein said partial eclipsing means is located intermediate the first and second apertures .

4. An ophthalmoscope according to claim 1, 2 or 3, wherein said partial eclipsing means comprises a baffle.

5. An ophthalmoscope according to claim 4, wherein said light directing means is associated with the baffle.

6. An ophthalmoscope according to claim 4 or 5, wherein said light directing means is mounted on the baffle.

5 7. An ophthalmoscope according to claim 5 or 6, wherein said light directing means is arranged to divert light on a first path along a second light path exiting the first aperture and constituting the exiting light path.

0

8. An ophthalmoscope according to claim 7 including another baffle located along the first light path between a light source and the first aperture.

5 9. An ophthalmoscope according to claim 8, wherein the other baffle has a free end which, along a line or plane extending generally parallel to the first light path, is coincident with an extreme end of said diverting, light directing means adjacent the sight

) path.

10. An ophthalmoscope according to claim 9, wherein the free end of the other baffle is coincident with but does not overlap the extreme end of said diverting,

5 light directing means.

11. An ophthalmoscope according to claim 9 or 10, wherein the free end of the other baffle is arranged to project into the first light path from a light source.

)

12. An ophthalmoscope according to any of claims 7 to 11, wherein said diverting light directing means comprises a mirror, prism or optic fibre light guide.

13. An ophthalmoscope according to any of claims 1 to 6, wherein said light directing means comprises a light source located intermediate the first and second apertures .

14. An ophthalmoscope according to claim 13, wherein the light source is associated with a baffle located intermediate the first and second apertures and arranged to transmit light directly along the path exiting the first aperture.

15. An ophthalmoscope according to claim 14, wherein the light source is mounted upon the baffle intermediate the first and second apertures.

16. An ophthalmoscope according to claim 13 or 14, wherein the light source is arranged to transmit light directly through the baffle and along the path exiting the first aperture.

17. An ophthalmoscope according to any preceding claim, wherein the generally parallel exiting or second light path, as the case may be, and the sight path are as close to one another as possible.

18. An ophthalmoscope according to claim 17, wherein the generally parallel exiting or second light path, as the case may be, and the sight path have portions thereof which are coincident with each other between the light directing means and first aperture.

19. An ophthalmoscope according to any preceding claim, wherein light from any light source is collimated.

20. An ophthalmoscope according to claim 19, wherein the light source is an integral component of the ophthalmoscope or is a separate, detachably removable component thereof.

21. An ophthalmoscope comprising:

means in which a first light path is defined;

a second aperture through which an user can view a subject eye along a sight path extending generally parallel to the second light path,

wherein the light diverting means partially eclipses the second aperture on the sight path along which an user can view a subject eye.

22. An ophthalmoscope according to claim 21, wherein the ophthalmoscope is lens-free.

23. An ophthalmoscope according to claim 21 or 22, wherein a baffle is arranged between the first light path and the second aperture.

24. An ophthalmoscope according to claim 23 including another baffle located between a light source and the light diverting means and/or the first aperture.

25. An ophthalmoscope according to any of claims 21 to 24, comprising a light source.

26. An ophthalmoscope according to claim 24 or claim 25 when dependent thereon, wherein the other baffle is located along the first light path between the light source and the first aperture.

27. An ophthalmoscope according to claim 24, 25 or 26, wherein the other baffle has a free end which, along a line or plane extending generally parallel to the first light path, is coincident with an extreme end of said light diverting means adjacent the sight path.

28. An ophthalmoscope according to claim 27, wherein the free end of the other baffle is coincident with but does not overlap the extreme end of said light diverting means.

29. An ophthalmoscope according to claim 27 or 28, wherein the free end of the other baffle is arranged to project into the first light path.

30. An ophthalmoscope according to any of claims 25 to

29, wherein the light source is an integral component of the ophthalmoscope or is provided as a separate, detachably removable component thereof.

31. An ophthalmoscope according to any of claims 21 to

30, wherein said light diverting means comprises a mirror.

32. An ophthalmoscope according to claim 31, wherein the mirror is inclined at substantially 45° to the first light path and/or the second light path.

33. An ophthalmoscope according to any of claims 21 to 30, wherein said light diverting means comprises a prism or a bent or angled section of a fibre optic, light guide device.

34. An ophthalmoscope according to claim 33, wherein said light diverting means comprises a light guide device which at least partially constitutes the first and/or second light path(s).

35. An ophthalmoscope according to any of claims 21 to 34, wherein said light diverting means is associated with a baffle.

36. An ophthalmoscope according to any preceding claim, wherein said means in which the first light path is defined, comprises a tube.

37. An ophthalmoscope according to claim 36, wherein at least the wall of the tube is opaque.

38. An ophthalmoscope according to claim 36 or 37, wherein the inner surface of the tube is non- reflective.

39. An ophthalmoscope according to claim 36, 37 or 38, wherein the first aperture is formed in the tube wall.

40. An ophthalmoscope according to any preceding claim, wherein the first aperture is circular.

41. An ophthalmoscope according to any preceding claim, wherein the second aperture is in a closed end of the tube.

42. An ophthalmoscope according to claim 41, wherein the closed end of the tube is an inclined roof of the tube .

43. An ophthalmoscope according to claim 41 or 42, wherein the second aperture is circular.

44. An ophthalmoscope according to any preceding claim, wherein said light directing means or light diverting means, as the case may be, overlaps the second aperture by 10% to 50% of the height thereof, preferably 20% to 30% of the height thereof.

45. An ophthalmoscope comprising:

means in which a first light path is defined;

means arranged to divert light from the first light path along a second light path exiting the ophthalmoscope through a first aperture and into a subject eye;

a second aperture through which an user can view a subject eye along a sight path extending generally parallel to the second light path; and

46. An ophthalmoscope according to claim 45 which is lens-free .

47. An ophthalmoscope according to claim 45 or 46 including means partially eclipsing the second aperture .

48. An ophthalmoscope according to claim 47, wherein said partial eclipsing means comprises said light diverting means .

49. An ophthalmoscope according to any of claims 45 to 48, wherein the baffle has a free end which, along a line or plane extending generally parallel to the first light path, is coincident with an extreme end. of said light diverting means adjacent the sight path.

50. An ophthalmoscope according to claim 49, wherein the free end of the baffle is coincident with but does not overlap the extreme end of said light diverting means .

51. An ophthalmoscope according to claim 49 or 50, wherein the free end of the baffle is arranged to project into the first light path from a light source.

52. An ophthalmoscope according to any of claims 45 to

51, wherein said light diverting means comprises a mirror, prism or optic fibre light guide.

53. An ophthalmoscope according to any of claims 45 to

52, wherein the generally parallel second light and sight paths are as close to one another as possible.

54. An ophthalmoscope according to claim 53 _r wherein the generally parallel second light and sight paths have portions thereof which are coincident with each other between the light directing means and first aperture .