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Y.-Z. Wang, G. Caniano, K. G. Locke, D. G. Birch; The Rate of Progressive Loss of Shape Discrimination Hyperacuity and Visual Acuity in Stargardt Macular Dystrophy. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3502.
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© ARVO (1962-2015); The Authors (2016-present)
Recent progress in understanding the pathogenesis of macular degeneration has led to potential new treatments for the disease. There is an increasing demand for new visual function tests that are more sensitive than current standards to monitor disease progression and to evaluate treatment effect. Our previous studies demonstrated that patients with macular degeneration have significant loss in global shape discrimination hyperacuity. In this study, we determined the rate of progressive loss of this hyperacuity in patients with Stargardt macular dystrophy (STGD).
Sixty-eight patients with STGD were selected on the basis of 20/200 or better visual acuity in at least one eye at their first visit. The average age at the first visit was 33±15SD years, and the average follow-up was 4.3±2.8SD years. Visual stimuli were circular shapes (radial frequency patterns). Shape discrimination hyperacuity was determined by using a two-alternative forced-choice paradigm. Each trial contained two intervals: one distorted circular pattern and the other undistorted pattern. Patients were asked to indicate which interval had the distorted pattern. A maximum likelihood fitting procedure was used to estimate the hyperacuity. Tests were conducted monocularly.
The cross-sectional data obtained from 110 eyes showed that, for visual acuity 20/50 (0.40 logMAR) or better, more visual function deficit was revealed by shape discrimination hyperacuity than by visual acuity. When compared to normal for the eyes with 20/50 or better acuity, the average loss of shape discrimination hyperacuity was 0.40 logMAR, while the average loss of visual acuity was 0.25 logMAR. For the eyes with visual acuity worse than 20/50, the average loss was 0.86 logMAR for both hyperacuity and visual acuity. The linear regression of the follow-up data obtained from 22 eyes with 20/50 or better visual acuity at the first visit revealed a loss of 0.058 logMAR per year for shape discrimination hyperacuity (n = 70, r = 0.63, p < 0.001) and 0.025 logMAR per year for visual acuity (n = 70, r = 0.37, p < 0.01).
These results demonstrate that shape discrimination hyperacuity is more impaired in early stages of macular degeneration and shows more rapid progression of loss than visual acuity, suggesting that it may be a more sensitive functional marker for the management of macular degeneration.
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