Nine-year Incidence of Visual Impairment in the Barbados Eye Studies
Received 24 October 2008; received in revised form 9 January 2009; accepted 12 February 2009. published online 04 June 2009.
Objective
To describe the 9-year incidence of visual impairment and primary causes of blindness among black participants of the Barbados Eye Studies (BES).
Design
Population-based prospective cohort study.
Participants
The BES followed a nationally representative cohort selected by simple random sampling, aged 40 to 84 years at baseline, with reexaminations after 4 years (Barbados Incidence Study of Eye Diseases [BISED]) and 9 years (BISED II). BISED II included 2793 (81%) of those eligible.
Methods
Cumulative 9-year incidence rates were estimated by the Product-Limit approach. The study was reviewed and approved by the institutional review boards of collaborating institutions.
Main Outcome Measures
Best-corrected visual acuity (VA) was assessed by the Ferris-Bailey chart, following a modified Early Treatment of Diabetic Retinopathy Study protocol. Low vision and blindness were defined by World Health Organization (WHO) criteria as VA <6/18 to 6/120, and <6/120, respectively, in the better eye, and by U.S. criteria as VA ≤20/40 and ≤20/200, respectively. Vision loss was defined as a decrease of 15 letters or more read correctly in the better eye between baseline and follow-up examinations.
Results
The 9-year incidence was 1.0% and 2.1% for blindness and 6.0% and 9.0% for low vision, by WHO and U.S. criteria, respectively. Older age at baseline was associated with higher incidence of low vision and blindness, reaching 23.0% (95% confidence interval [CI], 18.8–28.0) and 4.3% (95% CI, 2.7–6.9) at age 70 years or more, based on WHO criteria. The primary causes of incident bilateral blindness (U.S. criteria) in 126 eyes were age-related cataract (48.3%), open-angle glaucoma (OAG) (14.3%), combined cataract and OAG (6.3%), diabetic retinopathy (8.7%), and optic atrophy (7.1%). Age-related macular degeneration (2.4%) rarely caused blindness.
Conclusions
Incident visual impairment is exceedingly high in this population. Cataract, OAG, and diabetic retinopathy remain the major causes of blindness, underpinning the clinical and public health significance of these conditions in this and similar populations.
Financial Disclosure(s)
The author(s) have no proprietary or commercial interest in any materials discussed in this article.
Available online: June 4, 2009.
1Department of Preventive Medicine, Stony Brook University School of Medicine, Stony Brook, New York
3Chronic Disease Research Centre, Tropical Medicine Research Institute, University of the West Indies, Barbados, West Indies
4Wilmer Institute, The Johns Hopkins University, Baltimore, Maryland
Correspondence: Anselm J. Hennis, PhD, FRCP, Chronic Disease Research Centre, The University of the West Indies, Jemmott's Lane, Bridgetown, Barbados, West Indies
Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.
Supported by Grants EY07625 and EY07617 from the National Eye Institute, Bethesda, Maryland.
⁎ For group membership, see Leske MC, Wu SY, Hennis A, et al. Nine-year incidence of age related macular degeneration in the Barbados Eye Studies. Ophthalmology 2006;113:29–35.
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