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Brett G Jeffrey, Catherine A Cukras, Wadih M Zein, Amy Turriff, Brian Patrick Brooks; Retinal Function and Structure Correlations in ABCA4 Retinopathy. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3821.
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© ARVO (1962-2015); The Authors (2016-present)
Preparations for clinical trials of ABCA4 retinopathy require development of suitable outcome measures. The present study investigated correlations between retinal structure changes and function in ABCA4 retinopathy.
45 patients (12-63 yrs) with molecularly confirmed ABCA4 retinopathy were evaluated. Retinal structure was assessed from 30o OCT horizontal and vertical line scans centered on the fovea. The distance from the anatomic fovea to the start of the ellipsoid zone (EZ) band in the superior and nasal direction was calculated. Retinal sensitivity was measured using 2-color dark adapted MP1 perimetry to a reverse L-shape pattern, centered on the fovea and extending 15o nasally and 11o superiorly. Achromatic area, a quantitative measure of dsychromatopsia, was derived using a low color test. Visual acuity and ISCEV ERGs were recorded.
The EZ band could be identified and MP1 recorded in 33 patients (73%). The remaining subjects had either no EZ band and/or no MP1 response. Bland-Altman plots indicated good agreement between the OCT EZ band and retinal thresholds in determining the size of the non-seeing area along both horizontal (mean difference ± SD; -0.15 ± 1.3 deg) and vertical (-0.29 ± 0.8 deg) meridians. Two color dark adapted perimetry thresholds adjacent to the non-seeing area were mediated by rods only (n=20) or both rods and cones (n=13). The eyes with rod-mediated thresholds had smaller (p<0.05) areas of non-seeing retina (5.2 ± 2.3 deg) than eyes with mixed rod/cone thresholds (7.1 ± 2.0 deg). The size of the non-seeing area was correlated with achromatic area (p<0.005), scotopic ERG a-wave amplitude (p<0.003), cone ERG amplitude and implicit time (both p<0.01) after correction for multiple comparisons. Visual acuity formed a bimodal distribution with peaks at 20/32 and 20/160.
The size of the non-seeing area in ABCA4 retinopathy may be determined from structural changes in the OCT EZ band and the loss of dark adapted retinal sensitivity. Additionally, the size of the non-seeing area correlates with local changes in cone function (i.e. color vision) and full-field changes in both ERG rod and cone function. These results suggest close correlation between structure and function in ABCA4 retinopathy and that OCT, retinal sensitivity, color vision and ERG may be suitable and complementary outcome measures in clinical trials for ABCA4 retinopathy.<br /> Jeffrey IOVS abstract #1399, 2014
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