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R.A. Honkanen, B. Nemesure, S.Y. Wu, Y. Yoo, A. Hennis, M.C. Leske, The BESs Study Group; Intraocular Pressure (IOP) and the 9–year Risk of Open–Angle Glaucoma (OAG) in a Population of African Origin . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2346.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the relationship between baseline IOP and the 9–year incidence of OAG in the Barbados Eye Studies (BESs) cohort.
The BESs included 4,709 (84% participation) randomly selected residents of Barbados, W. I., 40–84 years at baseline. Surviving cohort members were re–examined at 4– and 9–years, respectively. This report is based on participants of African origin (n= 4,314 at baseline). OAG was determined by visual field plus optic disc criteria, after excluding other possible causes; IOP was not considered. Incidence of OAG was based on persons who developed OAG in at least one eye during 9–years, among those without OAG in either eye at baseline. Cumulative incidences were estimated through the product–limit approach. Cox regression models determined relative risk (RR) ratios with 95% confidence intervals (CI) for persons at different IOP levels at baseline.
The 9–year incidence of OAG (based on 125 incident cases) increased steadily with higher IOP, from 1.8% with IOP≤17 mmHg to 22.3% with IOP>25 mmHg. Among the 431 persons with baseline IOP>21 mmHg, incidence was 15.6%, vs. 2.8% with IOP<21mmHg, for an overall 9–year population incidence of 4.4% (95% CI: 3.7%, 5.2%). After adjusting for age, gender, hypertension and IOP–lowering treatment, incidence was significantly higher among those with IOP 21–23 mmHg at baseline, as compared to those with IOP≤17 mmHg (RR=5.4 (95% CI: 2.7, 10.5)). The corresponding RRs were 7.9 and 13.1 for baseline IOP 23–25 mmHg and >25 mmHg, respectively. While these RRs were high, most persons in the population have IOP<21mmHg and considerable overlap existed in the baseline IOP of those with and without incident OAG. The attributable risk (AR) was 37% for IOP >21 mmHg and 19% for IOP >25 mmHg.
This longitudinal study quantifies the long–term risk of OAG at different IOP levels, based on a population of similar ancestry to African–Americans. While these new data confirm the strong relationship between IOP and incident OAG, they highlight the role of OAG risk factors other than IOP.
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