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Cynthia Owsley, Mark Clark, Gerald McGwin, Eric C Strauss; Natural History of Rod-Mediated Dark Adaptation Over 2 Years in Eyes with Intermediate Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3690.
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© ARVO (1962-2015); The Authors (2016-present)
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.
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.
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).
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.
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