Abstract
Purpose: :
We have previously developed a highly reproducible method for assessing macular recovery time by measuring recovery of L-cone sensitivity after photostress. By this method, recovery time is significantly elevated in older subjects relative to younger. In this study, the MRT of early-to-intermediate dry AMD patients was compared to younger and older control subjects.
Methods: :
MRT after photostress was assessed in 44 eyes of 22 subjects, including 5 younger controls (aged 20-23; BCVA ≥ 20/20 in better eye), 6 older controls (aged 61-75; BCVA ≥ 20/40 in better eye), and 11 patients with early-to-intermediate dry AMD (aged 60-81; BCVA ≥ 20/40 in better eye). Each subject was tested 3 times within 2 weeks to assess reproducibility. After baseline assessment of L-cone threshold using the Roland Consult Dark Adaptometer, a photostress exposure sufficient to bleach 90-95% of cone photopigment was applied with a diffused fluorescent light source. Immediately following exposure, the recovery of L-cone sensitivity was monitored with the dark adaptometer. For each subject and trial, recovery half-life was estimated using an exponential recovery model. The effects of age and disease status on baseline cone threshold and recovery half-life were assessed via an exponential model with fixed effects for age and AMD and random effects for subjects.
Results: :
Mean ages of young controls, old controls, and AMD patients were 21.6, 64.0, and 70.2. Mean logMAR BCVA of young controls, old controls, and AMD patients were -0.05 (-0.16 - 0.0), 0.07 (-0.04 - 0.16), and 0.11 (-0.06 - 0.28) in their better eyes, and -0.04 (-0.14 - 0.0), 0.1 (0.02 - 0.18), and 0.25 (0.02 - 0.38) in their worse eyes. As described previously, old subjects had longer recovery times than young subjects. A bimodal pattern was observed in the AMD eyes, with a subset of eyes having normal recovery times and a second subset having significantly prolonged recovery times relative to old controls.
Conclusions: :
These results support our previous observation of longer recovery time in older compared to younger subjects. We note that a subset of early to intermediate dry AMD patients exhibit slower recovery than age-matched controls.
Clinical Trial: :
http://www.clinicaltrials.gov NCT01204541
Keywords: age-related macular degeneration • clinical research methodology • aging: visual performance