Total Retinal Pigment Epithelium Thickness and Reflectivity, in Relation to Histology and Vision, at the Aging-AMD Transition: ALSTAR2 Baseline.

Purpose

The retinal pigment epithelium (RPE) is critical in age-related macular degeneration (AMD) pathophysiology. We compare total RPE thickness (TRPET) and normalized reflectivity intensity (TNRR) on optical coherence tomography (OCT) among healthy aged and early AMD (eAMD) and intermediate AMD (iAMD) eyes, and to visual function.

Methods

Spectralis OCT volume scans from aged, eAMD, and iAMD eyes (per Age-Related Eye Disease Study [AREDS] 9-step) of the Alabama Study on Early Age-related Macular Degeneration 2 (ALSTAR2) baseline sample were automatically segmented for vitreous, nerve fiber layer (NFL), and total RPE (measured up to the centerline of the interdigitation zone) and manually corrected. TNRR was normalized with reference to vitreous and NFL within zones of the Early Treatment Diabetic Retinopathy Study (ETDRS) grid. Vision tests included rod-mediated dark adaptation (RMDA), a functional benchmark for AMD risk (reported as rod intercept time [RIT]), and other tests of rod- and cone-mediated function.

Results

Of 502 eyes of 502 participants (71.8 ± 6.1 years, 59.6% female participants), 252 were healthy, 147 had eAMD, and 103 had iAMD. TRPET was significantly thinner in iAMD compared with eAMD and healthy eyes (P < 0.001) and moderately correlated with longer RIT in all eyes (r = 0.12-0.35). TNRR was lower in iAMD eyes compared to eAMD and healthy eyes (P < 0.01); correlation with RIT was weaker but significant.

Conclusions

Reduced TRPET and TNRR in AMD and their correlation with RMDA are statistically significant due to the large sample. Whether they have practical utility for AMD detection will be learned from ongoing longitudinal studies. In ALSTAR2, non-RPE layers may contribute to delayed RMDA.