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Mae Gordon, Julia Beiser, J. Phillip Miller, Michael Kass, Feng Gao, ; The Ocular Hypertension Treatment Study (OHTS): Does Higher Long-Term IOP Variability Increase Risk Of Developing Primary Open Angle Glaucoma (POAG) in the Medication Group?. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3506.
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To determine if higher long-term IOP variability increases the risk of developing POAG among participants in the OHTS medication group (MED).
Analysis of baseline and follow-up IOP in 720 participants randomized to topical ocular hypotensive medication. Indices of IOP variability were: 1. standard deviation (SD), 2. maximum, 3. range, 4. coefficient of variation (CV) and percent change from baseline. Incident POAG was defined as confirmed visual field abnormality or optic disc deterioration of clinically significant magnitude attributed to POAG by an Endpoint Committee. Univariate and multivariate time dependent Cox proportional hazards models were used to estimate hazard ratios. Serial landmark models were used to estimate the C-index averaged over time. Covariates in multivariate models were baseline age, CCT, PSD, VCD and follow-up IOP.
In the MED group, 111 of 720 participants developed POAG in OHTS I and II (median f/up 13.0 yrs.); only SD (HR 1.21, p=0.024) and CV (HR. 1.19, p=0.045) independently increased the risk of developing POAG in multivariate models. The C-statistic was 0.755 for the “basic” multivariate model with covariates only and no measures of IOP variability. After adding SD to the basic multivariate model, the C-statistic increased from 0.755 to 0.766. After adding CV to the basic multivariate model, the C-statistic increased from 0.755 to 0.765.
In the MED group, higher long-term IOP variability, specifically SD and CV, independently increased the risk of developing POAG in the multivariate model. However, the addition of either SD or CV to the multivariate model did little to improve its predictive accuracy which was already at 0.755.
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