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Abstract #20045 Published in IGR 9-4
Incident open-angle glaucoma and intraocular pressure
Nemesure B; Honkanen R; Hennis A; Wu SY; Leske MC; Barbados Eye Studies GroupOphthalmology 2007; 114: 1810-1815
PURPOSE: To evaluate the role of baseline intraocular pressure (b-IOP) as a risk factor for incident open-angle glaucoma (OAG) in participants of African origin from the Barbados Eye Studies. DESIGN: Population-based nine-year cohort study. PARTICIPANTS: Three thousand two hundred twenty-two persons examined during the study period who were free of glaucoma at baseline and at risk of developing OAG during the nine-year follow-up. METHODS: Study protocols were standardized and included ophthalmic and other measurements, automated perimetry, applanation tonometry, fundus photography, and comprehensive ophthalmologic examination for those referred. The product-limit approach was used to estimate incidence. Relationships between b-IOP and incidence were evaluated by adjusted relative risk ratios (RRs) with 95% confidence intervals (CIs), based on Cox regression models. MAIN OUTCOME MEASURE: The nine-year incidence of OAG was based on both visual field and optic disc abnormalities, with ophthalmologic evaluations to exclude other possible causes. RESULTS: The overall nine-year incidence of OAG was 4.4% (95% CI, 3.7%-5.2%), and the mean (standard deviation) b-IOP among persons at risk was 18.0 mmHg (4.1). Among the 125 incident OAG cases, the mean b-IOP was 21.9 mmHg and 46% had b-IOP of > 21 mmHg. In contrast, the nonincident group had a mean b-IOP of 17.8 mmHg and only 12% had b-IOP of > 21 mmHg. Overall, OAG risk increased by 12% with each 1-mmHg increase in IOP (RR, 1.12; 95% CI, 1.08-1.16). Incidence steadily increased from 1.8% (95% CI, 1.2%-2.7%) for persons with b-IOP of ≤ 17 mmHg (referent group) to 22.3% (95% CI, 15.8%-31.1%) for those with b-IOP > 25 mmHg, resulting in an adjusted RR of 13.1 (95% CI, 7.1-24.1) among the latter group. The attributable risk for IOP of > 25 mmHg was 19%. Using 21 mmHg as a cutoff, the RR was 7.9 (95% CI, 3.8-16.2) and the attributable risk was 37%. CONCLUSIONS: After nine years' follow-up, the risk of OAG was positively related to IOP levels at baseline. Although persons with b-IOP of > 25 mmHg had a 13-fold RR of developing OAG, most cases arose with lower b-IOP. This study thus confirms the role of IOP as an influential risk factor, yet at the same time underscores its limitations in predicting OAG.
Dr. B. Nemesure, Department of Preventive Medicine, Stony Brook University, Stony Brook, NY 11794-8036, USA
Classification:
9.2.3 Open angle glaucoma with elevated IOP (Part of: 9 Clinical forms of glaucomas > 9.2 Primary open angle glaucomas)
