Association between intraocular pressure variation and glaucoma progression: data from a United States chart review.

PURPOSE: To evaluate whether greater intraocular pressure (IOP) variation between visits was associated with higher likelihood of glaucoma progression.

DESIGN: Cohort study.

METHODS: A five-year minimum of data (June 1, 1990 through January 22, 2002) was collected on 151 patients (302 eyes) from 12 United States specialty centers. A post hoc analysis of visual field (VF) progression, glaucoma medication, intraocular pressure (IOP), and other ocular data was conducted for two nonmutually exclusive cohorts based on retrospective data abstracted well after actual patient visits. Mean IOP and standard deviations (SD) were calculated before treatment (medication or surgery) or progression, whichever occurred first, and before progression regardless of treatment. IOP variables were assessed in a univariate fashion; Cox proportional hazards models evaluated glaucoma progression as an outcome measure and IOP SD as a main predictor, controlling for covariates.

RESULTS: In cohort 1 (55 patients; 84 eyes), mean age was 63 years (range, 37 to 85 years), 58% were female, and 19% of eyes underwent VF progression. In cohort 2 (129 patients; 251 eyes), mean age was 66 years (range, 19 to 88 years), 55% were female, and 27% of eyes underwent VF progression. Mean IOP was 16.5 mm Hg (IOP SD, 2.0 mm Hg), and 16.4 mm Hg (IOP SD, 2.7 mm Hg) in cohorts 1 and 2, respectively. Controlling for age, mean IOP, VF stage, and other covariates, each unit increase in IOP SD resulted in a 4.2 times and 5.5 times higher risk of glaucoma progression for cohort 1 (95% confidence interval [CI], 1.3 to 12.9) and cohort 2 (95% CI, 3.4 to 9.1), respectively.

CONCLUSIONS: IOP variability is an important predictor of glaucoma progression; SD is a convenient measure of variability to assess glaucoma progression risk.