Surgery – Diagnostic testing – Eye or testing by visual stimulus
Reexamination Certificate
2001-02-13
2003-12-02
Hindenburg, Max F. (Department: 3736)
Surgery
Diagnostic testing
Eye or testing by visual stimulus
Reexamination Certificate
active
06656131
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to systems and methods for detecting eye disease.
BACKGROUND OF THE INVENTION
Age-related macular degeneration (AMD) is the leading cause of blindness among people over the age of 50 in the western world. It is a bilateral, although asymmetric disease, and comes in two forms:
Dry or non-neovascular AMD is the more common and milder form of AMD, accounting for 85-90% of all AMD. The key identifier for dry AMD is small, round, white-yellow lesions in the macula. Vision loss associated with dry AMD is far less dramatic than in the case of wet AMD. There is currently no treatment available for dry AMD. It is estimated that as many as 14 million people suffer from dry AMD in the United States alone.
Wet AMD is less prevalent than the dry form, accounting for about 10-15% of AMD cases. The term wet denotes choroidal neovascularization (CNV), in which abnormal blood vessels develop beneath the retinal pigment epithelium (RPE) layer of the retina. Wet AMD is characterized by the development of choroidal angiogenesis which causes severe, and potentially rapid, visual deterioration. The visual distortion typically consists of perceiving straight lines as curved due to deformation of the retina in a region overlying the choroidal angiogenesis. The wet form accounts for about 60% of all cases of adult blindness in the United States. In the US alone there are 200,000 new cases of wet AMD every year and a total of 1.7 million blind people from AMD.
Treatment modalities for wet AMD include conventional treatments such as laser photocoagulation and newer treatment modalities such as PhotoDynamic therapy (PDT). Experimental treatments that are under current investigation include feeder vessel coagulation and Trans-pupillary ThermoTherapy (TTT). All these proven or experimental therapies may halt or slow progression of the disease only if detected at an early stage and will not reverse existing retinal damage. Therefore, early detection is crucial to prevent severe visual loss.
Since approximately 12% of dry AMD cases develop wet AMD and subsequent blindness within 10 years, a patient diagnosed with dry AMD must be routinely examined by an ophthalmologist once or twice a year, depending on the severity of his condition. The patient is usually also given a so-called “Amsler grid” for weekly self-examination at home for symptoms of wet AMD. The patient is advised to consult an ophthalmologist immediately in the event that symptoms are noticed. The Amsler grid and its modifications (such as the “threshold Amsler” or the “red Amsler”) have been displayed to be poor detectors of early changes associated with wet AMD for several reasons. One is the phenomenon of “filling-in” whereby the brain fills in missing parts in the pattern or corrects defects in the pattern. The subject thus fails to perceive a distorted pattern as being distorted. Another problem with the Amsler grid is the inability of patients to adequately fixate their vision on a fixed point while taking the test. The Amsler test also suffers from low compliance stemming from the non-interactive nature of the test.
The degree of visual deterioration is a function of the size of the lesion and its proximity to the fovea at the time of diagnosis. Although most lesions probably start outside the foveal area, 70% are already foveal and large (>1500 microns) at the time of diagnosis. It is therefore crucial to identify the lesions at the earliest possible stage, while they are still small and have not reached the fovea. It is known that 70% of lesions diagnosed as treatable become untreatable within less than three months, which indicates that the progression of the disease is relatively rapid. As many as 70-80% of patients with wet AMD are already ineligible for treatment when they first consult their ophthalmologist because the disease has progressed considerably. This is due to the poor validity of existing self-assessment methods for detecting an AMD-related lesion at an early stage, and the time lapsed between noticing the symptoms and seeing an ophthalmologist.
A reliable method for diagnosing wet AMD at the earliest possible stage, in conjunction with a referral system aimed at lowering the incidence of visual deterioration in this devastating disease, are imperative. If detected early, laser therapy to destroy the abnormal blood vessels may prevent additional vision loss. It is therefore crucial to detect the transition from dry to wet AMD as early as possible.
SUMMARY OF THE INVENTION
The present invention provides an eye test for detecting retinal lesions such as those associated with AMD or diabetes. The method involves showing a subject a first pattern displayed on a surface. The pattern may be, for example, one or more lines. The subject then fixates his vision on a point on the surface. The first pattern is hidden and a second pattern is displayed at a different location on the surface. The second pattern may be substantially identical to the first pattern, or the two patterns may be different. The subject is then asked to compare the second pattern and a predefined pattern. If the second pattern and the predefined pattern were identical, but the subject has perceived them to be different, this is indicative of a lesion of the retina. The subject indicates a region in the second pattern that appears to him to be different from the same region in the predefined pattern. The location of the lesion on the retina is determined from the location of the region in the second pattern on the surface relative to the point where the subject's vision was fixated. If the second pattern and the predefined pattern were not identical, but the subject reports that the two patterns were identical, this would indicate that he is not responding reliably to the test. Thus, the second pattern may be obtained by modifying the predefined pattern to simulate the predefined pattern as perceived by a person with an eye disease. For example, the second pattern may be obtained from the predefined pattern by displacing a component of the predefined pattern, removing a component of the predefined pattern, blurring a component, or altering an optical property of a component of the predefined pattern, such as color or intensity. Such modified patterns may also be used to demonstrate to subjects various types of visual disturbances associated with retinal lesions.
Since the subject will spontaneously shift his vision to the second pattern within about 200 msec after it appears, the subject may additionally or alternatively be asked to indicate whether any motion occurred of part of the second pattern relative to other parts of the second pattern as he shifted his vision, and if so, where in the second pattern the motion occurred. For example, a segment of a line that appears curved when in the periphery of the subject's field of vision may appear to straighten as the subject shifts his vision and brings the pattern into the center of his field of vision. This apparent movement at the particular location in the pattern as the subject shifts his vision is indicative of a retinal abnormality in the corresponding region of the retina.
The test is repeated several times, each time presenting the second pattern in a different region in the subject's field of view. This allows a retinal abnormality to be mapped on the retina.
In a preferred embodiment, the method is performed by displaying the patterns on a monitor screen such as a computer monitor, television, or stand-alone device. In this embodiment, the subject can be made to fixate his vision on a point of the screen by having him bring a cursor to the point on the screen using any computer input device such as a computer mouse, a keyboard, joystick or touch-screen. This causes the first pattern to disappear from the screen and for the second pattern to appear. The patterns may consist of one or more broken lines consisting of a plurality of segments. The subject indicates a segment in the second pattern that appears different to him than the correspo
Alster Yair
Azmon Barak
Rafaeli Omer
Eitan, Pearl, Latzer & Cohen Zedek LLP
Hindenburg Max F.
Notal Vision Inc.
Wingwood Pamela Lynn
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