Elsevier

Ophthalmology

Volume 111, Issue 1, January 2004, Pages 118-124
Ophthalmology

Four-year incidence of visual impairment: Barbados Incidence Study of Eye Diseases☆

https://doi.org/10.1016/j.ophtha.2003.04.002Get rights and content

Abstract

Objective

To describe the 4-year incidence of visual impairment and causes of blindness among black participants of the Barbados Eye Studies.

Design

Population-based incidence study.

Setting and participants

The Barbados Incidence Study of Eye Diseases (BISED) followed the cohort of the Barbados Eye Study (BES), a prevalence study based on a simple random sample of Barbadians 40 to 84 years of age. BISED included 3193 black participants from the original cohort (85% of those eligible).

Main outcome measures

Best-corrected visual acuity (Ferris-Bailey chart) at baseline and follow-up was measured according to a modified Early Treatment of Diabetic Retinopathy Study protocol. By use of World Health Organization (WHO) criteria, low vision and blindness for an individual were defined as visual acuity (VA) <6/18 to 6/120 and <6/120, respectively, in the better eye. By commonly used US criteria, low vision and blindness were defined as VA ≤ 20/40 and ≤ 20/200, respectively. Vision loss was defined as a doubling of the visual angle (i.e., decrease of 15 letters or more read correctly between baseline and follow-up examinations). Progression was defined as vision loss among those with low vision at baseline.

Results

On the basis of WHO criteria, the overall 4-year incidence was 3.6% (95% confidence interval [CI], 3.0%–4.4%) for low vision and 0.6% (95% CI, 0.4%–1.0%) for blindness. Incidence rates were higher using US criteria: 5.3% (95 % CI, 4.5%–6.2%) and 1.5% (95% CI, 1.1%–2.0%), respectively, reaching 21.5% and 7.3% for persons aged 70 years or older at baseline. One tenth of the cohort had vision loss, and 28.6% of those with low vision progressed. About one half of incident blindness was due to age-related cataract. Nearly one fifth was caused by open-angle glaucoma (OAG) alone or combined with cataract, and approximately 10% was caused by diabetic retinopathy (DR).

Conclusions

The incidence of visual impairment was high in this Afro-Caribbean population, particularly in older age groups, indicating the public health significance of visual loss for this and similar black populations. Cataract, OAG, and DR were among the leading causes of incident blindness, paralleling their high prevalence in this population.

Section snippets

Materials and methods

The Barbados Eye Studies, funded by the National Eye Institute, are a series of population-based investigations aimed at determining the prevalence, incidence, progression, and risk factors for major causes of visual loss in a large, predominantly African-origin population. The detailed study design and methods have been previously described.11, 12 The baseline prevalence study, the BES,11 was conducted between 1987 and 1992 and involved a random sample of Barbadian-born citizens, 40 to 84

Results

Of the 3427 BISED participants, 3193 self-reported their race as black. Of these, 3142 had best-corrected VA data from both baseline (BES) and 4-year follow-up (BISED) examinations, after excluding unreliable VA data caused by illiteracy (determined at the examination) or uncorrected measurements (at those home examinations where corrected VA was not possible). The median age of this population was 56 years, and 58% were female. Table 1 presents the 4-year incidence of visual impairment by

Synopsis

This report provides the first observed incidence estimates on visual impairment in a large population of African origin, as determined after searching the literature. The results indicate a high incidence of visual impairment in this black population, particularly at older ages. On the basis of the WHO criteria, for every person with bilateral blindness, there were approximately 3 others with unilateral blindness. By use of the WHO criteria, the overall cumulative 4-year incidence of bilateral

Acknowledgements

The authors thank the Barbados Eye Studies participants and the Ministry of Health, Barbados, West Indies, for their role in the study.

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    • Cited by (0)

    ☆

    Manuscript no. 220855.

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

    *

    See Appendix for membership of The Barbados Eye Studies Group.

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    Copyright © 2004 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.