WO2011042722A1

WO2011042722A1 - Improvements in and relating to ophthalmic instruments

Info

Publication number: WO2011042722A1
Application number: PCT/GB2010/051637
Authority: WO
Inventors: Adrian Carl Beasley
Original assignee: Keeler Limited
Priority date: 2009-10-05
Filing date: 2010-09-30
Publication date: 2011-04-14
Also published as: GB0917412D0; GB2474079A; GB2474079B

Abstract

An ophthalmic instrument such as an indirect ophthalmoscope comprises viewing optics through which, in use, an eye under examination is viewed by the user of the device, and image capture means (24; 124) for capturing an image of said eye, wherein the instrument includes a viewing screen (26, 28; 126, 128), positioned, in use, in the user's field of view, for enabling the user to see the image being detected by the image capture means.

Description

Title: Improvements in and relating to Ophthalmic Instruments Field of the invention

This invention relates to ophthalmic instruments, and more particularly to an ophthalmic instrument fitted with an image capture means, such as a camera.

Background to the invention

The invention is particularly, but not exclusively, applicable to indirect ophthalmoscopes. Indirect ophthalmoscopy, in particular binocular indirect ophthalmoscopy, is a procedure commonly used to examine the fundus of an eye. The technique involves using a hand-held condensing lens which is placed between the user and the subject. This lens produces an aerial image that is viewed through the viewing optics of the ophthalmoscope.

Typically, an indirect ophthalmoscope is head mounted and comprises a light source through which a beam is projected towards the eye under examination via the handheld condensing lens. The ophthalmoscope includes viewing optics, usually binocular viewing optics, through which the user can obtain a view of the image of the fundus of the eye under examination.

Certain types of indirect ophthalmoscope are equipped with video cameras for capturing video footage of the eye under examination. The captured footage can be used in the teaching of indirect ophthalmoscopy techniques to students. Typically this footage would be displayed on an external computer connected to the ophthalmoscope via a suitable cable. The camera is typically directed to a half-silvered mirror which is positioned in front of the viewing optics so as to reflect part of the light received from the eye under examination up into the camera whilst allowing the remaining light to pass through to the viewing optics.

In view of the separation between the half-silvered mirror and the viewing optics, the field of view of the camera can vary relative to that of the viewing optics in a way dependent upon the attitude of the ophthalmoscope on the user's head. The ophthalmoscope typically therefore has a mechanism for adjusting the angle of the half-silvered mirror so that the user can try to ensure that the images captured by the camera correspond to what is being viewed through the viewing optics. However, this can be a tricky procedure because the user has to look away from the viewing optics to see what is being displayed on the computer screen.

Summary of the invention

According to the invention, there is provided an ophthalmic instrument comprising viewing optics through which, in use, an eye under examination is viewed by the user of the device, and image capture means for capturing an image of said eye, wherein the instrument includes a viewing screen, positioned, in use, in the user's field of view, for enabling the user to see the image being detected by the image capture means.

Thus the user can view a high quality image through the viewing optics with or without using the image capture means. When the image capture means is being used, the user is also able to check the image detected by the image capture means using the screen. This enables the user readily to ensure that the appropriate image is being detected and displayed to others and/or recorded.

The viewing optics may have an eyepiece, in which case the screen is preferably situated adjacent the eyepiece.

This feature facilitates the quick comparison of the images visible through the viewing optics with that obtained by the image capture means.

Preferably, the viewing screen is carried on the instrument, and is preferably positioned above the eyepiece.

Preferably, the viewing screen is situated behind a lens to enable close viewing by the user. The lens thus allows the user to focus on the screen when the distance between the latter and the user's eye is less than the user's least distance of distinct vision. The viewing optics may have two eyepieces, as is the case with, for example, a stereoscopic instrument, in which case the viewing screen is preferably one of two such screens, each positioned adjacent a respective eyepiece.

Preferably, the image capture means comprises a camera, preferably a video camera. Preferably, the instrument is head mounted.

The viewing screen is particularly advantageous with such an instrument since it enables the user readily to see the captured image without having to move his/her head and thereby alter the captured image and/or the image visible via the viewing optics.

Preferably, the instrument comprises an indirect ophthalmoscope.

In this case the screen may be separate from the body of the ophthalmoscope and includes means for mounting and retaining the screen in a position, in use, in the vicinity of the hand held lens.

For example, the screen may be attached to the lens, or provided with a strap or band for attaching the screen to the user's forearm (on the side of the hand holding the lens). Such a band could be similar to the arm bands used for mounting personal music players on the arms of users who wish to listen to music while jogging.

The screen is positioned away from the user's eye but still in his/her field of view, through the viewing optics. Consequently this feature avoids the need for any accommodation lens in front of the screen.

The instrument may to advantage include recording means having a memory in which images captured by the image capture means are stored.

The separate screen, memory and recording electronics may be provided in a common housing which also contains a power supply for the screen, memory recording electronics and the image capture means (connected to the power supply) recording electronics and display screen by a cable.

Preferably, the viewing screen comprises an LCD, LED or OLED screen. Brief description of the drawings

Two embodiments of ophthalmic instrument, in accordance with the invention, will now be described, by way of example only, with reference to the accompanying drawings in which :-

Figure 1 is an isometric view of a first embodiment of ophthalmoscope in accordance with the invention;

Figure 2 is a corresponding view of a second embodiment of ophthalmoscope in accordance with the invention;

Figure 3 is a block circuit diagram of certain components of the ophthalmoscope of Figure 2, and also shows a possible modification to that ophthalmoscope;

Figure 4 is a schematic side view of the viewing optics and illumination optics of the ophthalmoscope; and

Figure 5 is a schematic view of part of the viewing optics of the ophthalmoscope. Detailed description

With reference to Figure 1, the first embodiment of ophthalmoscope in accordance with the invention comprises an indirect ophthalmoscope generally referenced 1 attached to the front of a headband 2 which enables the ophthalmoscope to be mounted on the head of a user. The rear of the headband 2 carries a battery pack 4 which provides power for operating a light source in the ophthalmoscope 1. The intensity of light emitted by that source can be controlled by intensity control 6 on the headband 2. The ophthalmoscope 1 also includes a video camera connected to a computer (not shown) via a USB cable 7 over which power for operating the camera is also supplied.

The ophthalmoscope 1 comprises a housing 8 in the general shape of an inverted T, which contains illumination optics (including the light source mentioned above) and binocular viewing optics.

The illumination optics are housed within the vertical stem of the housing 8 and comprise a light source 207 (Fig. 4) and an angled mirror 209 positioned under the light source to reflect light from the latter out through a window 10 in the front face of the housing 8. The mirror is positioned immediately above viewing optics 211 contained within the crosspiece 12 of the housing 8. Two side controls 14 and 16 enable the angle of that mirror to be adjusted.

The illumination and viewing optics (and associated controls) of the ophthalmoscope are as described in the present applicant's US Patent No. US 6280033, the contents of which are incorporated herein by reference.

An angled half- silvered mirror 18 is situated in front of the viewing optics on a mount which enables the angle of the mirror 18 to be adjusted by means of two side controls 20 and 22. The mirror 18 reflects light incident thereon up into the camera which is a digital video camera and is mounted within the stem of the housing 8 in a position immediately above the mirror 18. The adjustment provided by the controls 20 and 22 enables the user of the ophthalmoscope to adjust the field of view of the image detected by the camera so that it coincides as far as possible with what is being seen by the user through the viewing optics.

In use, 30% of the light incident on the mirror 18 is reflected up into the camera 24, most of the remaining 70% passing through the mirror to the viewing optics so that the mirror does not unduly degrade the image seen through the viewing optics. The illumination optics, viewing optics, and the arrangement of the camera and half- silvered mirror are substantially the same as the corresponding parts of the current applicant's existing VANTAGE PLUS DIGITAL™ ophthalmoscope. The camera 24 is a USB2 powered board camera which has a USB socket via which it is connected to the cable 7.

However, the output of the camera 24 is split so that the composite video signal from the camera is also supplied to driving circuitry for operating a pair of LCD screens 26 and 28 so that each screen acts as a local display of the image captured by the camera. Since the viewing optics in the instrument 1 are binocular, they provide left and right eyepieces, and each of the screens 26 and 28 is positioned immediately above, and hence adjacent, a respective eyepiece.

A converging lens (not visible in the view of Figure 1) is situated in front of each of the two LCD screens to enable the user readily to focus on the displayed image from a small distance.

The positioning of the screens 26 and 28 relative to the eyepieces means that the user can readily check whether the image detected by the camera corresponds to the image which is being viewed through the viewing optics. Alternatively, the user could use the images displayed on the screens 26 and 28 in the course of the examination of an eye, and can revert to using the viewing optics if the user needs to see a better quality image.

In any event, the screens 28 and 26 enable the user to ensure that the images being displayed on the computer connected to the ophthalmoscope via cable 7 (or being saved on the computer for subsequent use) correspond to the images on which the ophthalmic examination is based.

Turning to Figure 2, the second embodiment of ophthalmoscope in accordance with the invention has many features which correspond to those of the first embodiment and these are denoted by the reference numerals of Figure 1 raised by 100.

As is the case with the first embodiment, the camera 124 has an output which is split to provide a signal for the LCD display screens 126 and 128. However, instead of having a USB socket, the ophthalmoscope 100 includes a slot for a solid state memory card 115.

With reference to Figure 3, the camera 124 produces a composite video output which is split at 152 so that it can be fed in parallel to the displays 126 and 128 and to a video analogue to digital converter (ADC) 154 which converts the output from the camera into a digital data stream. It will be appreciated that corresponding components on the block diagram of Figure 3 are present in the first embodiment, and that the block representing the screens also represents their associated driving ciruitry.

The output of the video ADC 154 is supplied to a microprocessor 156 which is programmed to compress the input data stream and convert it into computer readable files in a known way. The output of the microprocessor 156 is connected to a card reader (not shown) via which data can be written into the memory card 150. The microprocessor 156 includes an additional input 158 for a command signal from a record button 160 which is situated in a suitable position on the ophthalmoscope housing 108 and which enables the user to commence or interrupt recording of footage captured by the camera 120. An output 162 of the microprocessor 156 is connected to an indicator LED 164 which illuminates every time the system is in record mode. As can be seen from Figure 3, the power supply for the camera, the display, the ADC, the microprocessor, the memory card and the indicator 164 is obtained from the battery pack 104 in this case.

In Figure 3, the block 166 is part of the modified version of the second embodiment. In the modified version, the memory card 150 is replaced by an internal, on-board memory, and the microprocessor 156 is connected to a computer interface 166 which is, in turn, connected to a USB socket. No external view of this ophthalmoscope has been provided because it is not substantially different from the view shown in Figure 1.

The modified version will record data onto the memory 150 for subsequent transfer to a computer along a USB cable (e.g. 7), the computer treating the ophthalmoscope as a mass storage device in this case. The provision of a memory on the instrument (or in a removable memory device such as a solid state memory card) avoids the need to communicate with a computer as the image is being captured. Thus, when in use, the instrument does not have to be connected to a computer via a cable which may be inconvenient and even pose a tripping hazard. Nor does the instrument need a radio link (which may be prone to interruption) with the computer. Images are not transferred to the computer in "real time", but for some applications this is not critical.

Examples of such applications are tele medicine where the images/videos will be sent to a third party for analysis/diagnosis; record keeping where the recorded images/video are kept for comparison to subsequent examinations for monitoring progress of condition or effectiveness of treatment; database accumulation to provide reference images/videos across a large number of patients; or record keeping as support to a doctor later challenged to have not identified a condition which develops later.

With reference to Figure 4, the illumination optics comprise a light bulb or LED 207, at the top of the housing 8, and an angled mirror 209 positioned underneath the light source so as to reflect light from the latter out through the window 10 in the front face of the housing. The mirror is positioned immediately above the viewing optics 211 (situated in the cross piece of the housing).

With reference to Figure 5, the viewing optics 211 comprise a pair of laterally spaced mirrors 213 and 215 which are mounted on triangular mirror blocks (217 and 219). The mirrors 213 and 215 are angled so as to direct light travelling into the viewing optics through the mirror 18 (along the viewing paths 221 and 223) horizontally outwards to the reflective surfaces of the mirrors 225 and 227 mounted on triangular mirror blocks 229 and 231 which have apertures (233 and 235) to allow the light to reach the mirrors 225 and 227. Further apertures (237 and239) in the blocks 229 and 231 enable the light reflected by the mirrors 225 and 227 to travel to eyepieces (not shown) situated behind the platform 241 on which the mirror blocks are mounted. The spacing between the mirrors can be adjusted in order to adjust the stereopsis of the ophthalmoscope.

Claims

An ophthalmic instrument comprising viewing optics through which, in use, an eye under examination is viewed by the user of the device, and image capture means for capturing an image of said eye, wherein the instrument includes a viewing screen, positioned, in use, in the user's field of view, for enabling the user to see the image being detected by the image capture means.

An instrument according to claim 1, in which the viewing optics have an eyepiece, and the screen is situated adjacent the eyepiece.

An instrument according to claim 2, in which the viewing screen is carried on the instrument.

An instrument according to claim 3, in which the viewing screen is positioned above the eyepiece.

An instrument according to claim 2 or claim 3, in which the viewing screen is situated behind a lens to enable close viewing by the user.

An instrument according to any of the preceding claims, in which the viewing optics has two eyepieces, the viewing screen having one of two such screens, each positioned adjacent a respective eyepiece.

An instrument according to any of the preceding claims, in which the image capture means comprises a camera.

An instrument according to claim 7 in which the camera is a video camera.

An instrument according to any of the preceding claims, in which the instrument is head mounted.

10. An instrument according to any of the preceding claims, in which the instrument comprises an indirect ophthalmoscope.

11. An instrument according to claim 10, when appended to claim 1, in which the screen is separate from the body of the ophthalmoscope and includes means for mounting and retaining the screen in a position, in use, in the vicinity of a hand held lens for use with the ophthalmoscope.

12. An instrument according to any of the preceding claims, in which the instrument includes recording means having a memory in which images captured by the image capture means are stored.

13. An instrument according to claim 12, in which the separate screen, memory and recording means are provided in a common housing which also contains a power supply for the screen, memory, recording means and the image capture means, the image capture means being connected to the recording means and display screen by a cable.

14. An instrument according to any of the preceding claims, in which the viewing screen comprises an LCD, LED or OLED screen.

15. An instrument according to any of the preceding claims, in which the instrument includes a head band for mounting the instrument on the head of a user.