Abstract
Purpose :
How does rod-mediated dark adaptation (RMDA) change over time in eyes with intermediate age-related macular degeneration (AMD)? This information will be useful in assessing the candidacy of RMDA as a potential outcome in evaluating interventions to prevent advanced AMD or to arrest its progression.
Methods :
Inclusion criteria were persons ≥50 yo with at least 1 eye with intermediate AMD (multiple large confluent drusen area ≥0.5 disk area, with or without increased or decreased RPE pigmentation), designated as the study eye; fellow eye with intermediate AMD, geographic atrophy or choroidal neovascularization; BCVA in study eye of 20/100 or better. AMD presence was determined by evaluation of color fundus photographs by a masked, trained grader. RMDA was assessed in the study eye at baseline after a 76% photobleach using a computerized dark adaptometer with targets centered at 5° on the superior vertical retinal meridian. Thresholds were measured over time until sensitivity recovered to a value of 5.0 X 10-3 scotopic cd/m2 . Time (minutes) to this event was defined as the rod-intercept (RI). The protocol was repeated at 6, 12, 18 and 24 months post baseline. For each eye a linear regression model was used to estimate the relationship between RI and time over 2 years. Slopes from these models were compared with respect to demographic and other variables.
Results :
30 eyes from 30 adults of European descent (mean age 74.2 yr, SD 6.6) were tested. There was no loss to follow-up. 7 of 30 eyes at baseline had RIs at or near ceiling (>25 min) that remained at ceiling over 2 years. For the remaining 23 eyes, mean slope was 0.18 (SD 0.23). The predicted RI increased on average by 4.3 min over two years (SD 5.6), ranging from a slight decrease of 1.4 minutes to an increase of 18.0 minutes. Variables at baseline associated with eyes having higher slopes (higher rate of RI increase over time) were age (p=0.020), smoking (p=0.017), and AMD family history (p=0.073).
Conclusions :
Most intermediate AMD eyes exhibited RMDA slowing over 2 years, averaging a more than 4-minute RI increase. Some eyes at baseline had RIs at ceiling that remained there over 2 years. Characteristics known to be strong risk factors for AMD and its progression (age, smoking) were associated with greater RMDA delay over 2 years.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.