Referenced scans improve the repeatability of optical coherence tomography angiography measurements in normal and glaucoma eyes

Aim To compare the repeatability of peripapillary perfusion density and flux index measurements on referenced and non-referenced optical microangiography (OMAG) scans in normal, glaucoma suspect and glaucoma eyes. Methods In a cross-sectional study, 48 eyes (33 subjects) underwent three repeat, non-referenced peripapillary OMAG scans in the same session and 43 eyes (25 subjects) underwent three referenced peripapillary OMAG scans. In the referenced scan group, repeat scans (second and the third scan) were acquired exactly on the baseline (first) scan using the 'track to prior scan' option on the device. Repeatability estimates of the mean and four-sector (temporal, superior, nasal and inferior) OMAG measurements on the non-referenced and referenced scans were assessed using within-subject coefficient of repeatability (CRw) and variation (CVw). Results CRw (%) of peripapillary perfusion density measurements (range: 2.0-4.1) on non-referenced scans were significantly higher than that on referenced scans (range: 1.4-2.7). CVw (%) on non-referenced and referenced scans ranged from 1.7 to 3.1 and from 1.2 to 2.1, respectively . CRw of flux index on non-referenced and referenced scans ranged from 4.4 to 5.8 and from 3.6 to 4.8, respectively. CVw on non-referenced and referenced scans ranged from 4.1 to 5.2 and from 3.3 to 4.5, respectively. Conclusions Repeatability estimates of OMAG measurements were better on referenced scans compared with non-referenced scans. Perfusion density measurements had lower variability than flux index. OCTA-measured perfusion density of referenced scans is preferable for monitoring vascular change in glaucoma