Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Reexamination Certificate
2000-03-08
2001-08-28
Manuel, George (Department: 3737)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
Reexamination Certificate
active
06280033
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to indirect ophthalmoscopes.
BACKGROUND TO THE INVENTION
In diagnostic and operative retinal practice, binocular indirect ophthalmoscopy is widely accepted as a fundamental method of examination of the retina of an eye. Typically, an indirect ophthalmoscope includes illuminating optics for illuminating the retina and viewing optics through which the image of the retina is viewed, and is mounted on a headband which enables it to be attached to the head of a user. The ophthalmoscope is used in conjunction with a hand held condensing ophthalmoscopy lens which the user positions between the viewing optics and the eye under examination so as to form an image of the retina between the lens and the viewing optics.
Compared with direct ophthalmoscopes, indirect ophthalmoscopes provide a relatively wide field of view and bright illumination of the retina under examination. However, this view is of a relatively low magnification.
It has been proposed to improve the magnification of an indirect ophthalmoscope by re-configuring the viewing optics so that the latter act as telescopes. However, this increases the complexity of the viewing optics and can adversely affect the size and weight of the ophthalmoscope. In addition, such an ophthalmoscope is no longer suitable for providing low magnification views.
SUMMARY OF THE INVENTION
According to the invention, there is provided an indirect ophthalmoscope for use in the observation of an eye, the ophthalmoscope comprising viewing optics through which, in use, at least part of said eye is viewed, light from the eye travelling to and through the viewing optics along a viewing path, wherein the ophthalmoscope includes a lens so mounted thereon as to be movable between an operative position, in which it is situated in said viewing path so as to refract light from the eye under examination, and an inoperative position, in which the lens is situated clear of the viewing path.
Thus the movable lens can enable the user to alter the size of image viewed through the viewing optics. If the viewing optics incorporate telescopic systems, the lens may, for example, be a diverging lens which reduces the magnification of the final image.
Preferably, however, the lens is a converging lens which, when in its operative position, acts as a magnifying lens for the image viewed through the ophthalmoscope.
When this lens is in its operative position, and the image formed directly by the hand held ophthalmoscopy lens is closer to the movable lens than the focal length of the latter, the movable lens acts as a magnifying glass which creates an enlarged virtual image of the retina further away from the viewing optics than the image formed by the ophthalmoscopy lens. This enables the user to see a focused image of the retina from a closer position than would be possible without the movable lens.
Preferably, the movable lens is a meniscus lens, preferably of a power of approximately +3 dioptre.
The lens may to advantage be mounted in front of the viewing optics so that, when in its operative position, it is interposed between the viewing optics and the eye under examination.
Preferably, the lens is pivotally mounted on the front of the ophthalmoscope so that movement between the operative and inoperative positions is achieved by pivoting the lens.
In this case, the lens is conveniently connected to a manually operated control member, preferably a rotary member, movable to cause said pivotal movement.
Preferably, the lens is mounted on the ophthalmoscope through a mounting bracket.
Preferably, the ophthalmoscope is a binocular device, the viewing optics being one of a pair of such viewing means for enabling an eye under examination to be viewed along corresponding left and right eye viewing paths, wherein the lens, when in its operative position, is situated in both viewing paths.
Preferably, the ophthalmoscope is attached to mounting means (for example a headband or headgear) for mounting it on the head of a user.
Another advantage of the movable lens is that it can be retrofitted to existing ophthalmoscopes without having to make any adjustment or modification to their viewing optics. In addition, since the ophthalmoscope can be positioned closer to the eye under examination, the user will obtain a better three-dimensional image (if the ophthalmoscope is a binocular device) because of the greater angle of convergence of the left and right eye viewing paths of the viewing optics on the retina under examination.
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patent: 5526074 (1996-06-01), Volk
patent: 5629747 (1997-05-01), Miyake
patent: 5793524 (1998-08-01), Luloh
patent: 5838421 (1998-11-01), Pedack
patent: 0 065 750 (1982-12-01), None
Keeler Limited
Lee Mann Smith McWilliams Sweeney & Ohlson
Manuel George
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