Factors related to the 4-year risk of high intraocular pressure: the Barbados Eye Studies.

OBJECTIVE To evaluate the 4-year risk of high intraocular pressure (IOP) and associated factors in a black population without glaucoma at baseline. DESIGN Population-based incidence study. PARTICIPANTS Random sample of Barbados residents aged 40 to 84 years. After 4 years, 3427 (85%) were reexamined. MAIN OUTCOME MEASURES Development of elevated IOP (using percentile-based definitions) among individuals with an IOP of 21 mm Hg or lower and no glaucoma at baseline. Associations were evaluated using polychotomous logistic regression. RESULTS At baseline, 2856 participants did not have glaucoma or suspected glaucoma: 361 had an IOP higher than 21 mm Hg or received treatment, and 2495 had an IOP of 21 mm Hg or lower and no treatment. At follow-up, only 58% of the 361 participants remained free of glaucoma and had an IOP higher than 21 mm Hg, whereas 30% had an IOP of 21 mm Hg or lower. Among the remaining 2495 participants, the incidence of IOP higher than 21 mm Hg or treatment (80th percentile) was 12.9% (95% confidence interval, 11.7%-14.3%). Using other definitions of elevated IOP, estimates ranged from 1.5% to 11%. Incidence increased with age, with rates 2.5 times higher at 70 years or older than at ages 40 to 49 years. Factors associated with high IOP included age, baseline IOP, hypertension, and blood pressure. Whereas participants with an IOP between 21 mm Hg and 28 mm Hg had higher blood pressure readings, those with an IOP of 21 mm Hg or lower or an IOP higher than 28 mm Hg had similar values. CONCLUSIONS Definitions of high IOP based on percentiles may be more applicable than those based on arbitrary values. Older individuals with a higher baseline IOP were more likely to develop elevated IOP after 4 years. Although blood pressure was also associated with high IOP, the relationship may be nonlinear.