Quantification of Geographic Atrophy using Spectral Domain Optical Coherence Tomography in Age-Related Macular Degeneration.

Abstract Purpose To compare geographic atrophy (GA) area and enlargement rate measured with SD OCT to fundus autofluorescence (FAF), color fundus photography (CFP), and infrared reflectance (IR) imaging. Design; Retrospective, multicenter, natural history case series. Participants 70 eyes with GA from 48 participants were included. Methods Participants underwent SD OCT, FAF, CFP, and IR imaging at baseline and 12 months in the study eye. SD OCT images were graded for GA area using two distinct criteria: 1) complete retinal pigment epithelium and outer retinal atrophy (cRORA) and 2) hypertransmission through Bruch’s membrane. Areas were measured with SD OCT using a custom developed tool that allows for mapping areas of retinal layer loss on SD OCT cross-sectional scans with co-registered IR images.Circularity Index was calculated from area and perimeter. SD OCT images were also assessed for presence of reticular pseudodrusen, outer-retinal tubules, and hyporeflective wedge-shaped bands. Area of GA was measured in mm2 from FAF, CFP, and IR images. Main Outcome Measures GA mean baseline area and enlargement rate measured with two SD OCT criteria, FAF, CFP, and IR. Results At baseline, the mean GA area was 6.9 (SD 4.7) mm2 using the SD OCT cRORA criteria and 7.3 (SD 4.7) mm2 using the SD OCT hypertransmission criteria. The mean annual enlargement rate of GA was 1.6 (SD 1.1) mm2 using the SD OCT cRORA criteria and 1.5 (SD 1.0) mm2 using the SD OCT hypertransmission criteria. When comparing both SD OCT grading criteria to FAF, CFP, and IR, there were no statistically significant differences in baseline area or annual enlargement rate of GA. Circularity index was identified as the risk factor for increased annual enlargement rate. Conclusions Measuring GA using retinal layer morphology provides a novel means of obtaining area measurements. Area measurements tend to vary based on criteria used and are comparable to other imaging modalities.