Focal electroretinogram and microperimetry testing of photoreceptor‐retinal pigment epithelium function in intermediate age‐related macular degeneration

Abstract

Purpose To compare the performance of focal electroretinogram (FERG) and fast mesopic microperimetry in evaluating macular function of intermediate age‐related macular degeneration (iAMD) subjects with preserved visual acuity. Methods Cross‐sectional, observational study. Participants with drusen >125 µm and VA ≥80 ETDRS letters and age‐ and sex‐comparable healthy subjects were consecutively enrolled in the study. Three photopic FERG recordings of the central 9° of the macula with luminance modulated stimuli flickering at 42.5 Hz and a fast mesopic microperimetry with a custom pattern of 3 central (CS) and 3 paracentral (pCS) stimuli at 1.2° and 6° from fixation were acquired. Results Overall, 112 eyes of 77 participants (age 73.0 ± 7.1 years, 47 iAMD eyes) were analysed. Mean FERG amplitude, CS and pCS (all p < 0.05) were lower in the iAMD group. A significant association was observed between FERG amplitude and iAMD (OR 9.58, p < 0.001) in multiple logistic regression analysis. Z‐scores of FERG were lower than microperimetry in iAMD (p = 0.002) but not for healthy participants. AUC of the ROC curve was greater for FERG than microperimetry (0.895 versus 0.644 and 0.675, both p < 0.05). Conclusion Focal ERG objectively measures a cumulative response originating from the photoreceptor‐RPE complex of the central 9° of the macula and demonstrated high accuracy in identifying decreased central macular function in iAMD patients with preserved visual acuity, performing better than fast mesopic microperimetry. Focal ERG should be considered a reliable technique for measuring retinal sensitivity of iAMD patients.