Effect of Testing Frequency on the Time to Detect Glaucoma Progression With Optical Coherence Tomography (OCT) and OCT Angiography

center dot PURPOSE: To determine how the frequency of testing affects the time required to detect statistically significant glaucoma progression for circumpapillary retinal nerve fiber layer (cpRNFL) with optical coherence tomogra-phy (OCT) and circumpapillary capillary density (cpCD) with OCT angiography (OCTA).center dot DESIGN: Retrospective, observational cohort study.center dot METHODS: In this longitudinal study, 156 eyes of 98 patients with glaucoma followed up over an average of 3.5 years were enrolled. Participants with 4 or more OCT and OCTA tests were included to measure the longitu-dinal rates of cpRNFL thickness and cpCD change over time using linear regression. Estimates of variability were then used to re-create real-world cpRNFL and cpCD data by computer simulation to evaluate the time required to detect progression for various loss rates and different test-ing frequencies.center dot RESULTS: The time required to detect a statistically sig-nificant negative cpRNFL and cpCD slope decreased as the testing frequency increased, albeit not proportionally. cpCD detected progression slightly earlier than cpRNFL. Eighty percent of eyes with a cpCD loss of -1%/y were detected after 6.0, 4.2, and 4 years when testing was per-formed 1, 2, and 3 times per year, respectively. Progres-sion in 80% of eyes with a cpRNFL loss of -1 mu m/y was detected after 6.3, 5.0, and 4.2 years, respectively.center dot CONCLUSIONS: cpRNFL and cpCD are comparable in detecting progression. As there were only small changes in the time to detect progression when testing increased from 2 to 3 times per year, testing twice per year may provide sufficient information for detecting progression with either OCT or OCTA in clinical settings. (Am J Ophthalmol 2023;245: 184-192.(c) 2022 Elsevier Inc. All rights reserved.)