Comparison between en face structural spectral-domain and swept-source OCT angiographic scans for the detection of persistent choroidal hypertransmission defects in AMD

Abstract

Purpose : Persistent choroidal hypertransmission defects (hyperTDs) were first described using en face spectral-domain OCT (SD-OCT) structural scans and subsequently studied using swept-source OCT angiography (SS-OCTA) scans. SD-OCT angiography (SD-OCTA) scans had not been previously used for the detection of these hyperTDs. To determine if SD-OCTA structural scans could provide similar results to SS-OCTA structural scans for the detection and measurement of hyperTDs, we analyzed same day images of the same patient on both instruments.

Methods : In this prospective OCT study, patients with age-related macular degeneration (AMD) and hyperTDs underwent SD-OCTA and SS-OCTA imaging at the same visit using the 6X6 mm scan patterns. The SD-OCTA scan consisted of 350 A-scans per B-scans and 350 B-scans along the y-axis, each B-scan repeated twice at each position. The SS-OCTA scan consisted of 500 A-scans per B-scans and 500 B-scans along the y-axis, each B-scan repeated twice at each position. En face images were generated from a slab with boundaries extending 64 to 400 µm beneath Bruch’s membrane. Two graders independently evaluated all en face structural images for the presence of persistent hyperTDs, which are defined as having a greatest linear dimension of ≥ 250 µm. At each visit, the number and area of all hyperTDs were obtained from both SD-OCTA and SS-OCTA scans. The square root of the total areas of the hyperTDs were compared.

Results : A total of 40 eyes from 32 subjects had SD-OCTA and SS-OCTA images taken on the same day. The number and total areas of hyperTDs for the two modalities were highly correlated, with correlation coefficients of 0.971 and 0.999, respectively. The mean number of hyperTDs were 4.2 ± 3.1 for the SD-OCTA and 4.5 ± 3.3 for the SS-OCTA scans, while the mean square root of the total hyperTD areas were 1.13 ± 0.63 mm for the SD-OCTA and 1.17 ± 0.65 mm for the SS-OCTA scans. Because of the strong correlation the small differences between the two scan patterns were statistically significant (P values <0.05), however, they should not be considered clinically significant.

Conclusions : The number and size of hyperTDs were strongly correlated between the SD-OCTA and SS-OCTA scans. This suggests that a single SD-OCTA scan pattern can be used for both structural and angiographic assessment of disease progression in AMD.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.