Comparison and Repeatability of High Resolution and High Speed Scans from Spectralis Optical Coherence Tomography...

The purpose of this study was to evaluate and compare the repeatability of optical coherence tomography angiography (OCTA) derived retinal vascular quantitative metrics using high resolution (HR) versus high speed (HS) acquisition modes.

Macular 4.4 × 2.9-mm OCTA images from normal, healthy volunteers were captured using both HR (768 A-scans × 256 B-scans) and HS (384 A-scans × 256 B-scans) acquisition protocols. Vessel density and vessel length density of the superficial capillary plexus and deep capillary plexus, as well as choriocapillaris flow deficit were computed. In a subset of eyes, the OCTA scans were repeated twice 2 days later and the same metrics were recomputed to assess repeatability, using intraclass correlation coefficients and coefficient of variation (CV).

Comparison of measurements between HR and HS acquisitions in 41 healthy eyes showed statistically significant differences for all quantitative metrics (P < 0.01). However, no significant differences were observed among the three repeated scans (one on day 1 and two on day 3) obtained with each of the acquisition modes. The CVs ranged from 0.01 to 0.03 with the HR mode and 0.01 to 0.04 with the HS mode. The intraclass correlation coefficients (ICCs) among measurements were similar and high for both HR and HS modes, ranging from 0.844 to 0.949.

HR and HS OCTA acquisition modes both yielded repeatable quantitative metrics for the retinal circulation and the choriocapillaris. However, despite a similar field, the HR and HS derived measurements differed significantly.

To establish OCTA imaging in clinical and research practice, standardized and repeatability image analysis are necessary.