Progressive Decline of Central Retinal Function In Early AMD: a 36 months longitudinal study by focal electroretinogram

Abstract

Purpose : To evaluate longitudinal changes in central retinal cone function of patients with early age-related macular degeneration (AMD).

Methods : Focal cone-mediated electroretinograms (fERGs) from the central retinal region (18 deg centered on the fovea, 41 Hz sinusoidally flickering stimulus) longitudinally recorded from 31 patients (mean age 65, range 55 -70 years) with early AMD (stage 2 of Ferris et al, Ophthalmology, 2013) were retrospectively evaluated. Patients had a visual acuity ≥ 20/40 at baseline and were tested 3-6 times, at least six months apart, over a time interval of 32-36 months. Standard clinical and multimodal imaging procedures were performed for each patient at yearly intervals. fERG amplitudes were plotted as a function of time on either an absolute (microVolts) or a relative (%) scale. Relative slopes of fERG amplitude vs time (assuming linear progression) were calculated for each patient.

Results : Mean relative fERG slope as a function of follow-up time was - 9%/year (range - 7 to- 12%, p < 0.01). The fERG slopes were independent of age, number and size of drusen at baseline. They were positively correlated with visual acuity at baseline, being more negative with lower baseline acuities (r =0.6, p 〈 0.05). No significant changes in fundus appearance and visual acuity were found over the same time interval.

Conclusions : fERG amplitude of early AMD patients shows a significant progressive decline over a three year interval, despite stable clinical picture. The decline tends to be faster in patients with partially reduced baseline acuity. The results support the use of the fERG as a surrogate functional measure of early AMD progression as well as an outcome measure in clinical trials of neuroprotection.

This is a 2020 ARVO Annual Meeting abstract.