Clinical Factors Associated With Long-Term OCT Variability in Glaucoma

Abstract

To examine clinical factors associated with long-term optical coherence tomography (OCT)-measured retinal nerve fiber layer thickness (RNFLT) variability in glaucoma. Retrospective cohort study. Glaucoma eyes from DIGS/ADAGES with≥2-years and 4-visits follow-up were included. RNFLT variability was calculated per-visit as the absolute error of optic nerve head RNFLT residuals across longitudinal follow-up. Clinical factors examined included general demographics, baseline ocular measurements, prior and intervening cataract extraction (CE) or glaucoma surgery, scan quality, baseline RNFLT and RNFLT thinning rate, follow-up duration, visit/testing frequency, etc. Three multivariable linear mixed models (full model, baseline model, and parsimonious model) were fit to evaluate the effects of clinical factors on RNFLT variability, with ten-fold cross-validation to estimate real-world model performance. A total of 1140 eyes (634 patients) were included. The overall mean (95% CI) RNFLT variability was 1.51(1.45, 1.58) µm. Across different models, African-American race (β[standard error, SE] = 0.18[0.06]), intervening CE (β[SE] = 0.52[0.07]), intervening glaucoma surgeries (β[SE] = 0.15[0.03]), and more positive RNFLT thinning rate (β[SE] = 0.06[0.02] per 1um/year more positive) showed consistent association with greater RNFLT variability, whereas more frequent visits/testing (β[SE] = -0.11[0.05] per 1 visit/year higher) was associated with smaller RNFLT variability (P<0.05 for all). Relevant clinical factors affecting long-term RNFLT variability in glaucoma were identified. These data enhance the evaluation of longitudinal structural change. Increasing the testing frequency, especially in eyes at risk of higher measurement variability, and resetting of baseline imaging after intervening procedures may help to more reliably detect OCT progression.