Abstract
Purpose:
To evaluate the relationship between morphology and function in AMD by correlating disease severity on SDOCT scans with macular function measured by best-corrected visual acuity (BCVA), cone-mediated sensitivity (CMS), and rod-mediated dark adaptation (RMDA).
Methods:
Eyes with no retinal aging (N=15), normal aging (N=15), early AMD (N=15), and intermediate AMD (N=46) per the Beckman classification system were used from the baseline visit of the Alabama Study on Early Age-Related Macular Degeneration. After semi-automated SDOCT segmentation, macular volumes for Retinal Pigment Epithelium Drusen Complex (RPEDC) were calculated. SDOCT-based drusen volume and RPEDC abnormal thinning volumes (RAT) were calculated referenced to 15 healthy age-controlled eyes following the method of Farsiu et al Ophthalmology 2014. We measured BCVA via Electronic Visual Acuity tester, CMS by Humphrey Field Analyzer, and RMDA by AdaptDx dark adaptometer. RMDA was defined by the rod-intercept (larger values mean slower RMDA). Groups were compared using chi-square tests, t-tests, analysis of variance and non-parametric equivalents.
Results:
Better CMS is associated with greater RPEDC volume (r=0.344, p=0.0009) and less RAT volume (r=-0.312, p=0.003). Larger rod intercept correlated with lower RPEDC volume (r=-0.342, p=0.005) and greater RAT volume (r=0.280, p=0.023). On SDOCT, less drusen volume differentiated no aging from each of the other groups (all p<0.05), whereas greater RAT volume differentiated intermediate AMD from each of the other groups (all p<0.05). BCVA and CMS did not differ for eyes with and without subretinal drusenoid deposits (SDD), however the rod-intercept did differ (for 19 SDD eyes Mean 13.5, SD 7.0 vs. for 47 eyes without SDD Mean 10.2, SD 3.1, p=0.004). RAT volume was greater for SDD eyes vs eyes without SDD (p<0.0001).
Conclusions:
Decreased function relates to structural markers on SDOCT in AMD. Worse CMS and slower RMDA were related to greater RAT volume. Eyes with slower RMDA were also more likely to have smaller RPEDC volumes. If RPEDC includes the interdigitation of outer segments and RPE apical processes in healthy eyes and SDD in eyes with AMD, then slower RMDA might be related to structural abnormalities at the RPE-photoreceptor interface and/or of the RPE.