ASSESSING THE REPEATABILITY OF INNER CHOROID FLOW DEFICIT PERCENTAGE IN INTERMEDIATE AGE-RELATED MACULAR DEGENERATION AND CONTROLS: A Comparative Study Between Different Post-Processing Approaches.

Abstract

To assess repeatability of macular inner choroid flow deficit percentage in intermediate age-related macular degeneration and controls using various postprocessing approaches. Cross-sectional, observational study. The authors included 1) 22 intermediate age-related macular degeneration and 24 control eyes, with 2) age >50 years, 3) visual acuity >20/32, and 4) no additional ocular and systemic confounders. Participants underwent four consecutive 6 × 6-mm optical coherence tomography angiography scans (2 acquired at 100-kHz and 2 at 200-kHz speed; PLEX Elite 9000) for intrasession analysis. Same protocol was repeated after 30 minutes for intersession analysis. Three slabs of different thicknesses were generated underneath Bruch membrane (4-14, 4-19, 4-24 µ m). All slabs were processed with: 1) binarization-only using Phansalkar method (r = 4-15 pixels); 2) compensation + binarization; 3) averaging + binarization; 4) averaging + compensation + binarization. Inner choroid flow deficit percentage was measured within 3-mm and 5-mm circles, and measurements were repeated after excluding drusen areas. Repeatability was analyzed with generalized linear mixed-effects models, intraclass correlation coefficients, and Levene variance test. Most postprocessing approaches demonstrated high repeatability (intraclass correlation coefficient >0.75) with no significant test-retest differences ( P > 0.05). Compensation + binarization of 15- µ m slabs at 200 kHz showed the highest repeatability (intraclass correlation coefficient: 0.96-0.98). Excluding drusen did not significantly affect inner choroid flow deficit percentage measurements ( P > 0.05), showing increased intraclass correlation coefficients for 10-µm-thick and binarized-only slabs. Strong repeatability can be achieved with various postprocessing methods for assessing inner choroid flow deficit percentage, especially with compensation + binarization of 15- µ m slabs acquired at 200 kHz. Drusen removal does not seem to affect repeatability in intermediate age-related macular degeneration when using a swept-source device, except for specific settings. These results contribute to refining choriocapillaris assessment, paving the way for future applications.