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Athanasios Panorgias, Megan Tillman, Erich E Sutter, John S Werner; Adaptation recovery of the photopic multi-focal ERG in early and intermediate age-related macular degeneration. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3493.
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To test whether age-related macular degeneration (AMD) affects retinal recovery after fast light adaptation using the photopic multi-focal m-sequence technique.
Ten subjects with early (n=6) and intermediate (n=4) AMD [76.4 ± 8.1 years old (mean ± 1 S.D.), range: 61-86 years] were tested using the multi-focal ERG (mfERG). AMD classification was based on a clinical exam and fundus image review by a retinal specialist. ETDRS best-corrected visual acuity (BCVA) was between 20/16 and 20/32. Ten age-matched normal subjects (77.5 ± 8.1 years old, range: 61-88 years) without any ocular or retinal pathologies and ETDRS BCVA of 20/25 or better underwent the same mfERG testing. mfERGs were recorded using the VerisPro software (EDI) that supports extraction of retinal responses at different inter-stimulus intervals (ISIs) and different flash combinations. An m-sequence of 16, resulting in ~14-min recordings, was used. The stimulus consisted of 103 hexagons having a peak luminance of 2.66 cd●s/m2. The responses were grouped into macular and peripheral retinal areas. In the macular region, the stimulus subtended a ~10° radial area centered on the fovea. The peripheral stimulus formed a ring with inner and outer radii ~10° and 20°, respectively. Single-flash responses preceded by a double flash were extracted from the signal at varying ISIs and the single flash amplitude was plotted as a function of ISI (called the recovery function). The rate of recovery was defined by the slope of the linear regression equation fitted through the linear phase of the recovery function.
The AMD subjects showed, as expected, lower mfERG responses in the macular area. However, no statistically significant difference was found in the rates of recovery between AMD and normal subjects for both the macular and peripheral areas (two-way ANOVA, p=0.104, α=5%).
AMD is known to affect predominantly outer retinal structures (photoreceptors and RPE) and this is manifested on the retinal electrophysiological responses, especially in the macular area. The results, however, suggest that the disease does not affect the recovery rate of the remaining functioning cones after fast light adaptation.
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