Abstract
Purpose :
Our conceptual framework for how visual function changes from normal aging to early and intermediate AMD specifies that the first visual dysfunction in AMD is delayed rod-mediated dark adaptation (RMDA), impacting photoreceptor sustenance (eg retinoid re-supply), including changes in choriocapillaris and RPE, and appearance of lipoprotein containing deposits. While evaluating this framework requires a longitudinal analysis, this cross-sectional analysis compares RMDA and other visual functions (acuity, contrast sensitivity, light sensitivity) between aged normal, early and intermediate AMD eyes, providing insight as to the validity of our framework.
Methods :
ALSTAR2 is a prospective cohort study to examine functionally validated structural endpoints in normal aging and early and intermediate AMD. At baseline participants were recruited based on ICD10 codes in EHR. AMD disease presence and severity was determined via color fundus photos evaluated by a masked grader using the AREDS 9-step system. Visual functions evaluated were RMDA (5° eccentricity, 83% equivalent bleach), acuity and contrast sensitivity (photopic, mesopic), and light sensitivity for a 21-target grid in the macula (scotopic, mesopic, photopic) using S-MAIA and HFA.
Results :
N=482 eyes from 482 persons (M age 72, 60-90 years) were evaluated (60% women, 91% white). Delayed RMDA was the most common visual dysfunction present in 36% of eyes in normal aging, increasing in prevalence to 51% and 94% in early and intermediate AMD respectively (Table 1). The difference in the prevalence of other visual dysfunctions was considerably less than for RMDA. Using z-scores to standardize measures, the largest difference in function by AMD status and severity was for RMDA between aged normal and intermediate AMD. While other functions were reduced among intermediates compared to normal, all differences were less than half that of RMDA (e.g., scotopic light sensitivity=0.75 SD). Of all functions, RMDA also had the greatest difference between aged normal and early AMD (0.30 SD).
Conclusions :
Among the visual functions considered, the greatest difference between AMD and normal eyes is for RMDA. This finding provides indirect support for the hypothesis that RMDA is the first visual function impacted during the natural history of AMD, which will be examined longitudinally at the ALSTAR2 three-year follow-up visit.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.