Impact of Swept-Source OCT Angiographic Scanning Speeds on the Detection of Choriocapillaris Flow Deficits in Eyes With AMD

Purpose: The impact of swept-source optical coherence tomography angiography (SS-OCTA) scanning speeds (interscan times) on the quantification of choriocapillaris flow deficit percentages (CCFD%) was studied in eyes with nonexudative age-related macular degeneration. Methods: We conducted a retrospective review of 30 pairs of scans from 24 age-related macular degeneration subjects enrolled in an ongoing prospective SS-OCTA imaging study. Patients underwent imaging with same day scans at two scanning speeds: 100 kHz and 200 kHz (corresponding with 5.0-ms and 2.5-ms interscan times, respectively). Best practices for CC slab processing and CCFD quantification were implemented, and the compensation level was optimized for each scan. CCFD% measurements were obtained from the 3-mm and 5-mm fovea-centered circles. Results: The mean CCFD% measurements from the 3-mm fovea-centered circles for the 100-kHz and 200-kHz scans were 14.20% and 17.17% respectively, and 10.77% and 12.86% for the 5-mm circles. An agreement analysis showed a significant bias with mean values of 2.96% and 2.09% for the 3-mm and 5-mm circles. The limits of agreement extended predominantly in the positive direction with values of -1.96% to 7.89% and -0.60% to 4.78% in the 3-mm and 5-mm circles, respectively, that emphasize the systematically higher CCFD% recorded using the 200-kHz pattern. No confidence interval for the bias included zero, supporting the significant systematic bias across measurement strategies. Conclusions: SS-OCTA scanning speeds have a significant impact on CCFD% quantification, with slower speeds yielding a lower CCFD%, likely due to the detection of slower CC flow, because of the higher associated interscan times. Translational Relevance: When following and comparing choriocapillaris flow deficit percentage measurements over time, the same scanning speed should be used at each visit.