Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Subjective type
Patent
1996-03-22
1999-03-23
Dang, Hung Xuan
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Subjective type
351222, 351246, A61B 302
Patent
active
058867708
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to visual field examinations and is concerned with a device for use in such visual field examinations or multifixation campimetry, that is, a method of testing for diseases of the eye and brain, for example glaucoma, in which the eye under examination is encouraged to move in a controlled manner in order to position a fixed central test stimulus at known positions in the visual field. The invention also relates to a method of using the device.
DESCRIPTION OF THE RELATED ART
In our European Patent No. 164,981 there is disclosed an oculo-perimetric device, which is relatively cheap and which can be used by a patient without skilled assistance or by an examiner. With this device eye movements are controlled by a series of fixation targets positioned around a fixed central test stimulus in the form of a reference target spot, and the device consists of an extended area visual target having a large plurality of generally regularly, angularly and/or radially spaced apart individual target elements disposed around the central reference target spot across substantially the whole of the area within a predetermined radial separation from said reference target spot. The individual target elements are a predetermined pattern of numbers arranged so as to define a visually discernible predetermined sequence for fixing of an eye of the subject, in use of the device, on successive adjacent individual target elements, said central reference target element being formed and arranged so as to be visually more prominent than said individual target elements. The eye is fixed on each number in turn and, should the reference target element in the centre not be visible out of the corner of the eye, then a potential defect in the field of vision is likely. In this way a map of defective areas in the patient's field of vision can be drawn up. One difficulty with this test card is that it is required to be placed at a correct distance from the patient's eye and in the correct side-to-side and up-down orientation. The correct distance from the subject's eye is achieved by means of a rigid side arm, which is pivotably attached to one side of the chart at one end and to an eye-occluder at the other end. In the disclosed method, this was also achieved by moving the test card to and from the patient, from side to side, and up and down with the eye fixed on an `L` or `R` marking (for left or right eye respectively) until the central target spot disappears in the patient's blind spot.
Whilst in theory this method is appropriate, in practice the number of possible orientations of the card makes correct positioning difficult for the unskilled user and may thus result in incorrect results being obtained.
It is an object of the present invention to obviate or mitigate at least one of the aforementioned disadvantages.
It is a further object of the present invention to provide an improved visual field examining device which has greater and variable sensitivity compared with the aforementioned device, which makes it easier for an examiner to assess the subject's cooperation, and which allows a larger area of the visual field to be examined, and also the device may be used for purposes other than the detection of glaucoma.
SUMMARY OF THE INVENTION
Thus, in accordance with one aspect of the present invention, there is provided a device for use in the examination of the visual field of a subject, which device comprises a visual target pattern having a plurality of spaced individual fixation targets disposed in a predetermined configuration around a substantially central test stimulus and across substantially the whole of the visual target pattern, each individual fixation target incorporating sequence indicating means so as to define a visually discernible predetermined sequence for fixing of an eye of the subject, in use of the device, on selected individual fixation targets, the arrangement being such that, in use, actuation of the central test stimulus causes a preselected test stimuli
REFERENCES:
patent: 2576358 (1951-11-01), Pritikin
patent: 4737024 (1988-04-01), Damato
patent: 4995717 (1991-02-01), Damato
patent: 5061059 (1991-10-01), Horn
Dang Hung Xuan
University Court of the University of Glasgow
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