Short-term Test-Retest Variability of Macula and Optic Nerve Head Optical Coherence Tomography Angiography Measurements

Abstract

Purpose : To evaluate the short-term test-retest variability of optical coherence tomography angiography (OCTA) measurements at the macula and optic nerve head (ONH) regions obtained with the Spectralis SDOCT (Heidelberg Engineering).

Methods : Glaucoma and healthy subjects were included from a prospective longitudinal observational study. OCTA scans of the macula and around the ONH were obtained 5 times within up to 6 weeks with the Spectralis SD OCT. The “binary” metric from the OCTA Analytics research software was evaluated for the whole retina (WR), superficial (SVC) and deep (DVC) vascular complexes, representing the percentage of area covered by vessels for each slab (i.e., vessel density). Global peripapillary RNFL thickness was also measured at each visit with OCT. Variability was assessed by the coefficient of variation (COV) with bootstrapped 95% confidence intervals (CI). The standard deviation (SD) of the residuals from linear mixed-effects regression models nested at patient and eye levels for each cluster were also calculated and evaluated at different levels of disease severity, represented by peripapillary RNFL thickness.

Results : The study included 1,305 valid OCT and OCTA tests distributed over 262 short-term clusters from 116 eyes of 68 subjects (mean±SD age = 69.9±7.2 years). Eyes had a mean±SD RNFL thickness of 73.1±19.6µm (range: 28 to 123µm). The SVC vessel density at the ONH level had the highest correlation with RNFL thickness (rho = 0.55, P<0.001), with a mean±SD vessel density of 26±6% (range 10% to 38%). The COV (95%CI) for SVC, DVC, and WR were 11.5% (10.7-12.2%), 17.6% (16.5-18.6%), and 6.3% (5.9-6.7%) at the ONH level and 11.1% (10.3-11.8%), 12.1% (11.0-13.1%), and 7.3% (6.8-7.9%) for the macula region, respectively. For comparison, the COV for RNFL thickness for the same visits was 1.7% (1.4-2.0%). While higher variability was observed for DVC and WR vessel density at more severe levels of the disease, thinner RNFL had no statistically significant effect on the SD of the residuals of the vessel density at the ONH (P=0.941) or macula (P=0.158) regions at the SVC level.

Conclusions : Although a higher variability was observed with the OCTA metrics compared to RNFL thickness, at the SVC level, worse disease severity did not significantly increase the variability of the OCTA vessel density measurements at the macula and ONH regions.

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