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Y.–Z. Wang, C.E. Wilson, K.G. Locke, B.F. Godley; Screening for Early Age–Related Macular Degeneration (AMD) Using a New Shape Discrimination Chart . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3315.
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Purpose: We previously reported that a new shape discrimination test chart has the potential to be a useful screening tool for early AMD. In this study, we examined the efficacy of a wall–mounted version of this chart in screening for early AMD in a local community senior center. Methods: Fifty senior volunteers (mean age 70+/–7SD years, mean acuity 20/25) with no known retinal disease (self–report) participated in the study. The wall–mounted shape discrimination chart consists of 16 sets of radial frequency (RF) patterns. Each set had 4 patterns, 3 un–modulated and 1 modulated. The task was to indicate which of 4 patterns in a set was modulated (4AFC). The amount of radial modulation decreases from the top (10%) to the bottom set (0.13%) of the chart. Each subject also performed a 2AFC computerized shape discrimination test employing RF patterns with comparable parameters. All tests were performed monocularly. For a subset of subjects (n=22), fundus photos were taken and evaluated by a retinal specialist. Results: Twenty–two subjects were divided into 2 groups based on their fundus evaluation. Group 1 (n=10) showed normal fundus appearance. Group 2 (n=12) showed drusen in the macula, 7 only with small size (< 63 µm) drusen and 5 with at least one medium size (>= 63 µm) drusen. The mean visual acuity was 20/23 in both groups. For group 1, the mean+/–SD modulation threshold of the chart test was 0.33%+/–0.11, not significantly different from that of the computerized test (0.32%+/–0.07). For group 2, the mean threshold of the chart test was 0.40%+/–0.10, higher than that for group 1 (p=0.145). The mean threshold of the computerized test for group 2 was 0.41%+/–0.09, significantly higher than that of group 1 (p<0.022). Three out of 7 subjects with small size drusen and 4 out of 5 subjects with medium to large size drusen had significant deficits in performing the chart shape discrimination test, while only one subject in group 2 had visual acuity worse than 20/32. None of 22 subjects reported seeing distortion on the Amsler grid. Conclusions:While the presence of drusen may not affect visual acuity, it can significantly reduce shape discrimination sensitivity. The shape discrimination test may be useful in screening for patients with macular dysfunction associated with drusen or early AMD.
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