Elsevier

Ophthalmology

Volume 115, Issue 1, January 2008, Pages 85-93
Ophthalmology

Original article
Risk Factors for Incident Open-angle Glaucoma: The Barbados Eye Studies

https://doi.org/10.1016/j.ophtha.2007.03.017Get rights and content

Purpose

To evaluate risk factors for definite open-angle glaucoma (OAG), based on African-descent participants of the Barbados Eye Studies.

Design

Cohort study with 81% to 85% participation over 9 years’ follow-up.

Participants

We evaluated 3222 persons at risk, 40 to 84 years old, who did not have definite OAG at baseline.

Methods

Participants had standardized study visits at baseline and after 4 and 9 years, with structured interviews, blood pressure (BP), and other measurements. The ophthalmic protocol included automated perimetry, applanation tonometry, fundus photography, and comprehensive ophthalmologic examinations for those referred. Central corneal thickness (CCT) was measured in a subset at the 9-year examination. Incidence was estimated by the product-limit approach; relative risk ratios (RRs) with 95% confidence intervals (CIs) were based on Cox regression models with discrete time.

Main Outcome Measure

Nine-year incidence of definite OAG.

Results

Over 9 years, 125 persons developed definite OAG (incidence, 4.4%; 95% CI, 3.7–5.2). Baseline factors influencing risk were age (RR, 1.04; 95% CI, 1.02–1.05 per year); family history of glaucoma (RR, 2.4; 95% CI, 1.3–4.6); higher intraocular pressure (IOP) (RR, 1.12; 95% CI, 1.08–1.16 per mmHg); lower systolic BP (RR, 0.91; 95% CI, 0.84–1.00 per 10 mmHg); and lower ocular systolic, diastolic, and mean perfusion pressures (RR, 0.66; 95% CI, 0.54–0.80 per 10 mmHg higher mean perfusion pressure) (RR, 2.6; 95% CI, 1.4–4.6 for low mean perfusion pressure [<40 mmHg]). Thinner CCT was also associated with OAG incidence (odds ratio, 1.41; 95% CI, 1.01–1.96 per 40 μm lower).

Conclusions

This is the first report of risk factors for long-term OAG incidence; it is also based on a sizable number of new cases. Incidence was high in this African-descent population, where the established factors of older age, higher IOP, and family history contributed to risk. Additional predictors were vascular factors, including lower systolic BP, and particularly lower ocular perfusion pressures, which more than doubled risk. Thinner CCT was also a factor. These findings indicate a multifactorial etiology of OAG and suggest that similar risk factors apply across populations. Results are relevant for understanding OAG causation and identifying groups at high risk.

Section snippets

Background

The major aims of the BESs were to determine prevalence, incidence, progression, and risk factors for the main eye diseases in Barbados, West Indies, a country where most persons (>90%) are of African descent. The background and methods of this National Eye Institute-funded study have been reported previously.4, 5, 6, 7 In summary, the BESs include a cohort of 4709 persons, identified through a simple random sample of the country’s population, 40 to 84 years of age, with 84% participation. By

Results

As shown in Table 1, the 3222 persons at risk of developing definite OAG at baseline had a median age of 56.9 years, 41% were male, and 7% had a family history of glaucoma. Diabetes and hypertension were common, at 17% and 52%, respectively. The median IOP was 17.7 mmHg and the median CCT (among the subset with pachymetry) was 537 μm. Table 1 also provides descriptive data on the BP and ocular perfusion pressure values in this population.

Over the 9-year follow-up, 125 persons developed definite

Discussion

After a follow-up of 9 years, we found a high OAG incidence of 4.4% in this African-descent population, averaging about 0.5% per year.5 In comparison, data from European-derived populations, although based on a small number of incident cases, suggest rates of 0.1% to 0.3% per year.1, 2, 3 What is the explanation for the higher risk observed? Aside from a true difference in the magnitude of the risk, possible explanations include differences in OAG classification criteria, data collection

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    Supported by the National Eye Institute, Bethesda, Maryland (grant nos. EY07625, EY07617).

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