The Impact of Social Vulnerability on Structural and Functional Glaucoma Severity, Worsening, and Variability

Purpose To determine the association between social vulnerability index (SVI) and baseline severity, worsening, and variability of glaucoma, as assessed by visual field (VF) and optical coherence tomography (OCT). Design Retrospective longitudinal cohort study. Participants Adults with glaucoma or glaucoma suspect status in one or both eyes. VFs were derived from 7,897 eyes from 4,482 patients, while OCTs were derived from 6,271 eyes from 3,976 patients. All eyes had a minimum of 5 tests over follow-up using either the Humphrey Field Analyzer or the Cirrus HD-OCT. Methods SVI, which measures neighborhood-level environmental factors, was linked to patient addresses at the census tract level. Rates of change in mean deviation (MD) and retinal nerve fiber layer (RNFL) thickness were computed using linear regression. The slope of the regression line was used to assess worsening, while the standard deviation (SD) of residuals was used as a measure of variability. Multivariable linear mixed-effects models were used to investigate the impact of SVI on baseline, worsening, and variability in both MD and RNFL. We further explored the interaction effect of mean IOP and SVI on worsening in MD and RNFL. Main Outcome Measures Glaucoma severity defined based on baseline MD and RNFL thickness. Worsening defined as MD and RNFL slope. Variability defined as the SD of the residuals obtained from MD and RNFL slopes. Results Increased (worse) SVI was significantly associated with worse baseline MD (β = −1.07 dB, 95% CI: [−1.54, −0.60]), thicker baseline RNFL (β = 2.46 μm, 95% CI: [0.75, 4.17]), greater rates of RNFL loss (β = −0.12 μm, 95% CI: [−0.23, −0.02]), and greater VF variability (β = 0.16 dB, 95% CI: [0.07, 0.24]). Having worse SVI was associated with worse RNFL loss with increases in IOP (βinteraction = −0.07, [95% CI: −0.12, −0.02]). Conclusions Increased social vulnerability index score is associated with worse functional (VF) loss at baseline, higher rates of structural (OCT) worsening over time, higher VF variability, and a greater effect of IOP on RNFL loss. Further studies are needed to enhance our understanding of these relationships and establish their cause.