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P. I. Rauen, R. Jorge, H. Jägle, F. Gekeler, R. C. Siqueira, A. Messias; Recovery of the Electroretinogram b-Wave Amplitude After Bleaching in Early AMD. Invest. Ophthalmol. Vis. Sci. 2010;51(13):6194.
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There is psychophysical evidences for alterations of dark adaptation in early stages of age related macular degeneration (eAMD). This study aimed to examine the kinetics of dark adaptation using ganzfeld electroretinography (ERG) in patients with eAMD.
Eighteen eAMD patients (30 eyes) and 10 normally sighted subjects (CTRL) were included. eAMD patients showed either macular druses and/or foveal retinal pigment epithelium changes and preserved visual acuity (20/30 or better). ERGs were recorded using DTL electrodes in a ganzfeld-system (Espion E2 system; Diagnosys LLC). ERG waveforms to brief flashes (4 ms) with stimulus intensity of 0.01 cd.s/m2 (ISCEV ROD) were recorded before (pre-bleaching or baseline), and every 2 minutes after the exposure to a bleaching illumination (600 cd/m2 for 4 min) for 21 minutes to assess recovery.
Mean ± SD b-wave amplitude at baseline was 308.2 ± 51.6 µV in CTRL and 276 ± 11.2 in eAMD (P=0.08; t-Test). The response waveforms following bleaching exposure were diminished, and b-wave amplitude was kept below of 20% of the baseline amplitude for about 5 minutes, thereafter recovered at a rate of approx. 10% per minute in an exponential pattern. No statistically significant changes were observed for the b-wave amplitude ratio (post-bleaching/baseline) at any time-point during the recovery period. The mean ± SD time to reach 50% of baseline amplitude was 11 ± 2 min in CTRL and 12 ± 3 min in eAMD.
In our study, kinetics of dark-adaptation derived from ERG recordings were not statistically different between patients with early AMD and normal subjects.
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