Local Analysis of Visual Dysfunction and Retinal Structural Alteration in Non–Exudative Age–related Macular Degeneration

Abstract

Abstract: : Purpose: To report changes in local retinal function and structure in patients with non–exudative age–related macular degeneration (AMD). Methods: We recruited 5 patients with non–exudative AMD (mean age of 72 yrs and mean visual acuity of 20/50). Seven retinal loci in the central 7° were analyzed. Local functional assessment included Humphrey visual fields and multifocal ERGs (mfERG: VERIS system). Local structure was assessed by grading fundus photographs into one of three categories: normal, drusen, or pigment epithelial atrophy. This was also quantified by measuring thickness using a prototype instrument based on the Retinal Thickness Analyzer (RTA). All data were converted to log loss (in db) relative to the mean of a group of age–matched control subjects. Results: Eight of the 35 retinal loci were clinically normal, 8 showed drusen, and 19 had focal atrophy. Significantly decreased psychophysical sensitivity and significantly decreased ERG amplitudes were found in areas with retinal pathology. ERG implicit times were delayed in all 35 retinal loci, including clinically normal–appearing areas. Retinal thickness alterations were present at loci with and without visible fundus pathologies. Amplitude (F=3.26, P=0.05) and visual field sensitivity (F=9.78, P <0.001) were significantly related to fundus grade. Significant correlations were found only between mfERG amplitude log loss and implicit time log loss (r = –0.36, P = 0.04) and between mfERG amplitude log loss and Humphrey sensitivity loss (r = 0.53, P = 0.002). Conclusions: Local functional deficits and retinal thickness abnormalities were found in areas with visible retinal pathologies. Implicit time delay may reflect subclinical abnormality in AMD.

Keywords: age–related macular degeneration • electroretinography: clinical • visual fields