Regional Cone Function in Age–Related Maculopathy Evaluated by Focal ERG and Static Perimetry: Central Losses Not Linked to Morphological Changes

Abstract

Abstract: : Purpose: To assess regional cone function in age–related maculopathy (ARM) by focal eletroretinograms (FERGs) and static automated perimetry, and to compare functional with morphological changes at corresponding locations Methods: Twenty–six patients (mean age 68, SD 5 yrs) with ARM (stage 1 or 2) and preserved visual acuity (20/40 or better) as well as 12 age–matched controls were evaluated. FERGs were recorded in response to either a central (eccentricity: 0–2.25°) or a paracentral annular (2.25–9°) sinusoidally flickering (41 Hz) field, presented on a light–adapting background. Perimetric sensitivity was measured by Octopus central 10 degrees program. For each patient, mean sensitivity losses were calculated for both central (0–2.25°) and paracentral (2.25–9°) regions. Morphological changes at corresponding retinal locations were assessed by stereoscopic fundus photography and fluorescein angiography. Results: When compared to control values, mean central and paracentral FERG amplitudes of patients were reduced (by 41 and 28%, respectively, p < 0.05). Mean perimetric central and paracentral sensitivities were reduced (by 2.5 and 1.7 dB, respectively, p < 0.05). FERG and perimetric losses were greater (p < 0.05) for the central compared to the paracentral region. By contrast, morphological lesions (soft drusen and/or retinal pigment epithelium defects) involved to a greater extent (% of affected area) the paracentral compared to the central region (on average 33% versus 15%, p < 0.05). Conclusions: Results indicate that central cone dysfunction in ARM may not be linked to morphological changes, and suggest a disease sequence where neural retina is functionally affected before development of primary ARM lesions.

Keywords: age-related macular degeneration • electroretinography: clinical • perimetry