Date of Award

1-1-2020

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Lucian Del Priore

Second Advisor

Jimmy Zhou

Abstract

The purpose of this study was to characterize further, using swept-source (SS-) optical coherence tomography angiography (OCTA), the relationship between dry age-related macular degeneration (AMD) and the macular choriocapillaris (CC), which may have pathophysiologic and therapeutic implications. It included (1) a topographic analysis to determine if there is a significant relationship between dry AMD stage and macular CC perfusion, and (2) an investigation of the predictive value of macular CC perfusion with respect to geographic atrophy (GA) growth rate.

Study design was retrospective and cross-sectional. A database of 6x6 mm fovea-centered swept-source OCTA images of the CC from eyes with early, intermediate, and advanced dry AMD (56 eyes, 41 patients) was generated using automated and manual segmentation. In (1), these images were analyzed using algorithms described in the literature to assess CC perfusion deficit metrics (flow deficit percentage (FD%) and average flow deficit size). Regions were defined by concentric areas centered on the fovea: a 1 mm diameter area, 3 mm diameter ring, 5 mm diameter area, 5 mm diameter ring, and 6x6 mm whole image. Data were modeled using the generalized estimating equations (GEE) approach. In (2), OCTA images from the database having GA as well as corresponding autofluorescence (AF) structural imaging at multiple time points (13 eyes, 10 patients) were analyzed for CC perfusion deficit metrics. These were plotted against the square root transformation of average GA growth rate, determined by AF over periods up to 52 months.

Results of (1) showed that the relationship between age and CC FD% and average flow deficit size was statistically significant (p ≤ .05) in all regions of analysis. The relationship between dry AMD stage and FD% was statistically significant in the 5 mm ring, and between dry AMD stage and average flow deficit size in the 3 mm ring, 5 mm area, 5 mm ring, and 6x6 mm whole image. Results of (2) showed a significant positive linear correlation between CC perfusion deficit metrics (flow deficit %: Pearson’s r = .68; average flow deficit size: Pearson’s r = .69) and the square root transformation of average GA growth rate.

In conclusion, generation of a unique database of SS-OCTA imaging of the CC in all stages of dry AMD enabled an improved understanding of the relationship between CC perfusion and dry AMD. Specifically, this study found a statistically significant relationship between dry AMD stage and CC perfusion, most prominent in the more peripheral regions of the macula, and suggested that a positive linear correlation between CC perfusion deficit and the square root transformation of average GA growth rate holds over periods up to 52 months.

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