Computer-Based Method Aids Evaluation of AMD

The computer method could also vary low-, medium-, and high-contrast illumination targets for testing spatial vision, which might be useful for early detection of AMD.

The investigators, who are associated with Toronto Western Hospital's (Toronto, Canada) Vision Science Research Program, the Centre for Vision Research at Toronto's York University (Toronto, Canada) and the Department of Ophthalmology and Vision Sciences at the University of Toronto (Toronto, Canada), incorporated four features known to improve visual acuity into their computer-based evaluation method: high contrast; white optotypes (symbols, letters, or numbers used in vision testing ) on a black background to reduce intraocular scatter; proportional layout to reduce the effects of crowding; and multiple optotypes to minimize the effects of fixation instability and to maximize the likelihood of optotype detection.

They conducted three experiments: the first measured the best-eye acuity of 24 AMD patients using the ETDRS charts and three versions of the Tumbling E acuity test; the second compared two white E optotype tests with the ETDRS in 14 AMD patients; and the third measured probability summation in 20 people with normal vision. They concluded that a multiple-optotype, reversed-polarity test is most effective in estimating a patient's optimal visual acuity at baseline before vision rehabilitation interventions or surgery. The results of subsequent evaluations should help assess rehabilitation progress.

The study was published in the October 2007 issue of the journal Investigative Ophthalmology and Vision Science (IOVS). The authors pointed out that patients with early AMD might demonstrate reduced function, not for the high-contrast, high-illumination targets of standard clinical acuity tests, but for medium- and low-contrast targets. They concluded that their computer method, which allows testing for targets of varying contrast, might help specialists detect AMD early.

"Detection of potential visual acuity in patients with AMD is a crucial step in the clinical practice of vision rehabilitation. The ability to accurately estimate such potential will enhance results from vision rehabilitation interventions.” said Dr. Markowitz, who is a member of the Vision Rehabilitation Committee of the American Academy of Ophthalmology (San Francisco, CA, USA).


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Toronto Western Hospital
University of Toronto
American Academy of Ophthalmology