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

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.

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.

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.

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.

When following and comparing choriocapillaris flow deficit percentage measurements over time, the same scanning speed should be used at each visit.