Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Subjective type
Patent
1994-01-18
1995-07-04
Pellman Gross, Anita
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Subjective type
351243, A61B 302
Patent
active
054305101
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns equipment for testing visual acuity and/or visual sensitivity to spatial contrasts in humans, and a corresponding device and a manufacturing process for such a test.
Contrasts perceived by humans may be of two types, ie temporal or spatial. Temporal contrasts correspond to variations in the contrast over time, as for example the variations in luminosity of a rotating warning light. Spatial contrasts on the other hand concern variations in contrast independently of time, but extending in space, ie for example a scene including areas of different contrasts, such as gradations of colours or different shades of grey (going for example from deep black to a grey which is barely tinted).
The present invention concerns solely a test for determining sensitivity to spatial contrasts in humans. In the following description it is thus understood that the term "contrast test" in fact means "spatial contrast tests".
Recent clinical studies have shown that it would certainly be beneficial to determine visual sensitivity to spatial contrasts even in subjects having good visual acuity. This is because certain pathological ocular conditions such as cataracts, glaucomas, disorders of the cornea, etc may be detected at a very early stage, by means of a contrast test, when the visual acuity function is still little affected or not affected at all. When detected quite early, such diseases may be treated more effectively. Likewise, this study of sensitivity to contrasts enables certain surgical techniques to be evaluated, such as corneal grafts, etc.
Devices enabling sensitivity to contrasts to be studied in humans are already known. The patent FR-2,342.051 (Acadia Associates) describes for example a device for determining sensitivity to contracts comprising a binocular viewing assembly, in which a patient sees transparencies appear which include as optotypes letters on a white background. By causing the background luminosity to vary, different absolute contrasts are created for all the letters carried by one transparency. The minimal contrast perceived by the patient is then determined for each size of letter (ie each spatial frequency of the optotype).
All these measurements are then entered on a graph indicating the minimum contrast perceived by the patient as a function of the spatial frequency. This curve is then compared with a standard curve established for a healthy subject. Any variations in the curve of the patient with respect to the standard curve reveal pathological ocular conditions etc.
One of the main drawbacks of such a device is that it requires considerable time to be spent on examination, in particular in order to produce and analyse the graphs. Such a device is far too time-consuming and complex to use for routine utilization, during a conventional ophthalmological screening examination. In addition, such a test disconcerts the patient and it is sometimes difficult to enable him to understand its operation, which has, of course, an adverse effect on the quality of the examination carried out.
Devices of the same type as the one described in U.S. Pat. No. 4,365.873 (Ginsburg), which is in the form of a transparent sheet having a plurality of test areas distributed in the form of rows and columns, are also already known. Each column has test areas with the same contrast and each row test areas with the same spatial frequency.
The patterns of the test areas are produced by networks, ie an alternation of dark and light areas with given contrasts and spatial frequencies. These dark and light areas may be sinusoidal or square in shape and are either vertical or sloping. The transparent sheet is placed on a diffusing face of a light box. The patient is placed at a certain distance from the box and has to indicate, for each of the test areas seen, whether its network is vertical or sloping.
The practitioner then notes the minimum contrast level discerned as a function of the spatial frequency of the test area discerned. It is then necessary to trace, for each patient, his curve of sens
REFERENCES:
patent: 4365873 (1982-12-01), Ginsburg
patent: 4607923 (1986-08-01), Task et al.
patent: 4615594 (1986-10-01), Task
patent: 4789234 (1988-12-01), Ginsburg et al.
patent: 4800404 (1989-01-01), Ginsburg et al.
patent: 4968131 (1990-11-01), Lewis
"Augenheilkunde" Martin Reim--Stuttgart: Enke, 1985, ISBN 3-432-95401-9 2.17 Untersuchung der Kontrastwahrnehmung.
Gross Anita Pellman
Mai Huy
OPSIA
LandOfFree
Equipment for testing visual acuity and/or sensitivity to spatia does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Equipment for testing visual acuity and/or sensitivity to spatia, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Equipment for testing visual acuity and/or sensitivity to spatia will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-764012