Delays in rod-mediated dark adaptation in early age-related maculopathy

Objective: To determine whether there are disturbances in the rod-mediated kinetics of dark adaptation in early age-related maculopathy (ARM). Design: Comparative, observational case series. Participants: Twenty older adults with early ARM as defined by one or more large (>63 mum) drusen, focal hyperpigmentation, or both, but no choroidal neovascularization or geographic atrophy, and 16 adults in the same age ran ge with none of these fundus features. All participants had 20/25 visual ac uity or better in the tested eye. Methods: Dark adaptation functions were measured using a modified Humphrey Field Analyzer (Zeiss Humphrey Systems, Dublin, CA) to assess the rate of r od-mediated sensitivity recovery at 12 degrees on the vertical meridian in the inferior visual field after exposure to the equivalent of a 98% bleach, Baseline (prebleach) scotopic sensitivity, visual acuity, contrast sensiti vity, and photopic sensitivity were also measured. Main Outcome Measures: Rod-cone break; second and third components of rod-m ediated dark adaptation; time to baseline sensitivity; and baseline (preble ach) scotopic sensitivity. Results: Although their visual acuity was at least 20/25, patients with ear ly ARM on average exhibited deficits in almost all rod-mediated parameters of dark adaptation as compared with age-similar healthy participants. For e xample, the rod-cone break was delayed approximately 10 minutes in early AR M patients as compared with healthy participants. Age-related maculopathy p atients were more likely to fall outside the normal reference range for var iables representing dark adaptation kinetics than for steady-state visual f unctions such as scotopic sensitivity, For example, 85% of ARM patients fel l outside the normal reference range in at least one dark adaptation kineti c parameter, whereas only 25% of ARM patients fell outside the normal refer ence range for steady-state scotopic sensitivity. Conclusions: Rod-mediated kinetic parameters of dark adaptation, which refl ect the sensitivity recovery of the visual cycle, are disrupted early in AR M pathogenesis, Ophthalmology 2001;108:1196-1202 (C) 2001 by the American A cademy of Ophthalmology.