Choroidal vascularity index quantification in geographic atrophy using binarization of enhanced-depth imaging optical coherence tomographic scans

Purpose: To evaluate choroidal structural changes occurring over time in geographic atrophy (GA) secondary to age-related macular degeneration using choroidal vascularity index (CVI). Methods: Enhanced-depth imaging optical coherence tomography scans of 34 patients with GA and 32 control subjects were retrospectively analyzed. Data were collected at baseline and after a mean follow-up of 18.3 ± 8.3 months. Choroidal images were binarized using the ImageJ software, and the luminal area and stromal area were segmented. Cho- roidal vascularity index was defined as the ratio of luminal area to total choroid area. Results: Patients with GA showed significantly lower values of CVI, total choroid area, luminal area, and subfoveal choroidal thickness compared to control subjects (65.83 ± 3.95 vs. 69.33 ± 3.11, P , 0.001; 0.400 ± 0.239 mm2 vs. 0.491 ± 0.132, P = 0.006; 0.263 ± 0.152 mm2 vs. 0.340 ± 0.094, P = 0.002; 185.2 ± 79.8 mm vs. 216.8 ± 58.8 mm, P = 0.036, respectively). Best-corrected visual acuity was significantly correlated only with choroidal thickness (R = 20.509; P = 0.002). During the follow-up period in patients with GA, sub- foveal choroidal thickness decreased from 185.2 ± 79.8 to 152.2 ± 73.1 (P = 0.001), stromal area increased from 0.138 ± 0.090 mm2 to 0.156 ± 0.068 (P = 0.028), and CVI decreased from 65.83 ± 3.95 to 62.24 ± 3.63 (P , 0.001). Conclusion: This study showed for the first time that CVI is reduced in patients with GA, and that this metric further worsened during the follow-up period.