Comparison between Spectral-Domain and Swept-Source OCT Angiography for the Measurement of Persistent Hypertransmission Defects in Age-Related Macular Degeneration

Purpose Spectral-domain OCT angiography (SD-OCTA) scans were tested in an algorithm developed for use with swept-source OCT angiography (SS-OCTA) scans to determine if SD-OCTA scans yielded similar results for the detection and measurement of persistent choroidal hypertransmission defects (hyperTDs). Design Retrospective study. Participants Forty pairs of scans from 32 patients with late-stage nonexudative age-related macular degeneration (AMD). Methods Patients underwent both SD-OCTA and SS-OCTA imaging at the same visit using the 6 x 6 mm OCTA scan patterns. Using a semiautomatic algorithm that helped with outlining the hyperTDs, 2 graders independently validated persistent hyperTDs, which are defined as having a greatest linear dimension >= 250 mu m on the en face images generated using a slab extending from 64 to 400 mu m beneath Bruch's membrane. The number of lesions and square root (sqrt) total area of the hyperTDs were obtained from the algorithm using each imaging method. Main Outcome Measures The mean sqrt area measurements and the number of hyperTDs were compared. Results The number of lesions and sqrt total area of the hyperTDs were highly concordant between the 2 instruments (r(c) = 0.969 and r(c) = 0.999, respectively). The mean number of hyperTDs was 4.3 +/- 3.1 for SD-OCTA scans and 4.5 +/- 3.3 for SS-OCTA scans (P = 0.06). The mean sqrt total area measurements were 1.16 +/- 0.64 mm for the SD-OCTA scans and 1.17 +/- 0.65 mm for the SS-OCTA scans (P < 0.001). Because of the small standard error of the differences, the mean difference between the scans was statistically significant but not clinically significant. Conclusions Spectral-domain OCTA scans provide similar results to SS-OCTA scans when used to obtain the number and area measurements of persistent hyperTDs through a semiautomated algorithm previously developed for SS-OCTA. This facilitates the detection of atrophy with a more widely available scan pattern and the longitudinal study of early to late-stage AMD.