The local cone and rod system function in early age-related macular degeneration

To compare cone and rod system function in patients with early age- related macular degeneration (ARMD) and control group using multifocal electroretinogram (MERG) and perimetry, to investigate whether there is rod system dysfunction in the central retina in ARMD. Cone-mediated MERG, photopic sensitivity, rod-mediated MERG, and scotopic sensitivity in 16 eyes of control subjects and 24 eyes of early dry-form ARMD were measured with VERIS Science ^TM 4.0 and Octopus 101 perimetry. The latencies and average response densities of the summed responses and five ring retinal regions, average sensitivity of all locus and eight ring retinal regions in control eyes were compared with those in ARMD. Mean scotopic and photopic sensitivity of ARMD patients were significantly lower than that of normal controls. Sotopic sensitivity reduced more than photopic sensitivity and the greatest deficit was 2.5–5.0°. The amplitudes of N₁ and P₁ wave in one ring (5.0°) of rod MERG were significantly lower of ARMD patients than that of normal subjects. Our results suggest that rod function decreased and the parafoveal rod cells were predominantly damaged in ARMD. The rod function testing in macula may be a useful tool to diagnose and measure the fundus dysfunction of ARMD.