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A. V. Cideciyan, M. Swider, T. S. Aleman, S. B. Schwartz, E. A. M. Windsor, E. M. Stone, S. G. Jacobson; Evaluation of Central Visual Function Using a Foveo-Papillary Profile in Macular/Retinal Degenerations Caused by ABCA4 (ABCR) Mutations. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1396.
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© ARVO (1962-2015); The Authors (2016-present)
To determine properties of a test pattern to use with a fundus-controlled microperimeter (MP1, Nidek) designed to balance considerations of testing time, spatial resolution and applicability to a wide range of disease severity.
Sampling (every 0.5o) of vision occurred along the horizontal meridian extending between 0.5o and 16o nasal to the anatomical fovea. Patients with ABCA4-associated retinal degeneration (n=25, ages 11-60) were dilated and fully dark adapted, and red stimuli (0.43o diameter, 200 ms duration) were used on a red background (1 cd.m-2). Three-sample moving average was applied. In a subset (n=19), testing was repeated either on the same visit or on a second visit. 0 dB thresholds were excluded to avoid floor artifacts. Variability was defined with point-by-point differences between test and retest thresholds.
In 13 (52%) of the eyes, fixation was at the anatomical fovea and there was paracentral scotoma; remaining 12 eyes had central scotoma and extrafoveal fixation. Function was measurable in all eyes across a retinal region (7.3±3.4o) between the nasal retinal edge of the central or paracentral scotoma at 5.6o (±3.2o) and the temporal retinal edge of the physiological blindspot (pBS) at 13.4o (±1.4o). Immediately temporal (1-2o eccentric) to the pBS was the most appropriate location for estimating the test-retest variability due to the existence of a broad range of sensitivity values, often reaching normal limits (15/25 subjects), and the presence of steep local changes in sensitivity near the pBS. Pointwise test-retest variability was 6.1 dB (99% CI); absolute values of the test-retest differences were not significantly correlated with the sensitivity values (P=0.29).
Clinical trials in macular degenerations cannot depend entirely on standard free-viewing systems for outcome measures of visual function. MP1 allows testing in patients with unstable and/or extrafoveal fixation. A foveo-papillary profile sampled at 0.5o provides an effective tradeoff between test duration and spatial resolution in order to measure localized disease progression at or near central lesion boundaries in a wide range of ABCA4 disease severity. Our preliminary results suggest that sensitivity changes of ≥7 dB at individual retinal loci may represent a significant change in vision such as may occur due to the expansion of a central scotoma.
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