Prevalence and causes of visual impairment in The Barbados Eye Study

OBJECTIVE

To determine the prevalence and causes of low vision and blindness in a predominantly black population.

DESIGN

Population-based prevalence study of a simple random sample of Barbados-born citizens aged 40 to 84 years.

PARTICIPANTS

Four thousand seven hundred nine persons (84% participation).

METHODS

The standardized protocol included best-corrected visual acuity (with a Ferris-Bailey chart), automated perimetry, lens gradings (LOCS II), and an interview. Participants with visual acuity of worse than 20/30, other positive findings, and a 10% sample also had an ophthalmologic examination that evaluated the cause and extent of vision loss (resulting from that cause), if any.

MAIN OUTCOME MEASURES

Low vision and blindness were defined as visual acuity in the better eye between 6/18 and 6/120 and visual acuity worse than 6/120, respectively (World Health Organization [WHO] criteria).

RESULTS

Of the 4631 participants with complete examinations, 4314 (93%) reported their race as black, 184 (4%) reported their race as mixed (black and white), and 133 (3%) reported their race as white or other. Low vision was found in 5.9% of the black, 2.7% of the mixed, and 3.0% of white or other participants. Bilateral blindness was similar for black and mixed race participants (1.7% and 1.6%, respectively) and was not found in whites. Among black and mixed participants, the prevalence of low vision increased with age (from 0.3% at 40-49 years to 26.8% at 80 years or older). The prevalence of blindness was higher (P < 0.001) for men than women at each age group (0.5% versus 0.3% at ages 40-49 and 10.9% versus 7.3% at 80 years or more). Sixty percent of blindness was due to open-angle glaucoma and age-related cataract, each accounting for more than one fourth of cases. Other major causes were optic atrophy or neuropathy and macular and other retinal diseases. Few cases of blindness were due to diabetic retinopathy (1.4%), and none were due to age-related macular degeneration.

CONCLUSIONS

Using the WHO criteria, prevalence of visual impairment was high in this African-origin population, particularly at older ages. Most blindness was due to open-angle glaucoma and cataract, with open-angle glaucoma causing a higher proportion of blindness than previously reported. The increased prevalence of blindness in men may be due to the increased male prevalence of glaucoma in this population and warrants further investigation. Results underline the need for blindness prevention programs, with emphasis on effective treatment of age-related cataract and enhancing strategies for early detection and treatment of open-angle glaucoma.

Foveal avascular zone in diabetes mellitus

The foveal avascular zone was measured angiographically in 144 subjects with diabetic retinopathy and 27 control subjects. Statistical significance was defined as P < 0.01. Quantitatively, the foveal avascular zone was significantly smaller in control eyes (median = 0.405 mm2) than in eyes with diabetic retinopathy, and smaller in eyes with background diabetic retinopathy (BDR; median = 0.737 mm2) than in eyes with proliferative diabetic retinopathy (PDR; median = 0.866 mm2) and preproliferative diabetic retinopathy (PPDR; median = 1.001 mm2). Qualitatively, the contour of the foveal avascular zone in diabetic retinopathy was irregular (29.2% of eyes with diabetic retinopathy vs 3.7% of control eyes) with scattered round microaneurysms. Diabetic retinopathy is characterized by an irregular, large foveal avascular zone with scattered microaneurysms.

Neovascular glaucoma. Etiologic considerations

A review of 208 patients with neovascular glaucoma (NVG) is presented. The most common primary etiologic associations included retinal venous obstructive disease (36.1%), diabetic retinopathy (32.2%), and carotid artery obstructive disease (12.9%). Systemic arterial hypertension was present in 51% and diabetes mellitus was noted in 46% of all patients. Among the 25 bilateral cases of NVG, 24 occurred in patients with diabetic retinopathy. Women comprised 65% of patients with NVG secondary to diabetes, and 57% of the venous obstruction group, while men accounted for 74% of cases in which NVG occurred secondary to carotid artery obstructive disease. Overall, 97% of eyes with NVG had a disease process that produced extensive retinal ischemia and preceded the onset of iris neovascularization. Patients with NVG, but without an obvious precipitating fundus condition, should be suspected of having severe carotid artery obstructive disease.

Diabetes, hypertension, and central obesity as cataract risk factors in a black population. The Barbados Eye Study

OBJECTIVE

The increased cataract prevalence of black populations, especially of cortical cataract, remains unexplained. The authors evaluate the relationships of diabetes, hypertension, and obesity patterns to lens opacities, by age, among 4314 black participants in the Barbados Eye Study.

DESIGN AND PARTICIPANTS

Prevalence study of a random sample of the Barbados population, ages 40 to 84 years (84% participation).

MAIN OUTCOME MEASURES

Associations with age-related lens changes (grade > or = 2 in the Lens Opacities Classification System II at the slit lamp) were evaluated in logistic regression analyses by age (persons < 60 years and > or = 60 years). Results are presented as odds ratios (OR) with 95% confidence intervals.

RESULTS

Of the 1800 participants with lens changes, most had cortical opacities. Diabetes history (18% prevalence) was related to all lens changes, especially at younger ages (age < 60 years: OR = 2.23 [1.63, 3.04]; age > or = 60 years: OR = 1.63 [1.22, 2.17]). Diabetes also increased the risk of cortical opacities (age < 60 years: OR = 2.30 [1.63, 3.24]; age > or = 60 years: OR = 1.42 [1.03, 1.96]); additional risk factors were high diastolic blood pressure (age < 60 years: OR = 1.49 [1.00, 2.23]) and higher waist/hip ratio (all ages: OR = 1.36 [1.00, 1.84]). Diabetes was also related to posterior subcapsular opacities. Glycated hemoglobin levels were positively associated with cortical and posterior subcapsular opacities. Overall, 14% of the prevalence of lens changes could be attributed to diabetes.

CONCLUSIONS

The high prevalence of cortical opacities was related to diabetes, hypertension, and abdominal obesity, which also are common in this and other black populations. Interventions to modify these risk factors, especially in populations in which they are highly prevalent, may have implications to control visual loss from cataract, which is the first cause of blindness worldwide.

Prevalence of lens opacities in the Barbados Eye Study

OBJECTIVE

To present population-based data on type and extent of age-related lens opacities in the predominantly black population of the Barbados Eye Study.

DESIGN

Prevalence study.

SETTING AND PARTICIPANTS

The Barbados Eye Study included 4709 participants (84% of those eligible), who were identified from a random sample of Barbadian-born citizens aged 40 to 84 years.

DATA COLLECTION

Lens gradings at the slit lamp, obtained with the use of the Lens Opacities Classification System II.

MAIN OUTCOME MEASURE

Prevalence of posterior subcapsular, nuclear, and cortical opacities (defined as a grade > or = 2 in either eye), as well as prevalence of any lens changes (including history of previous cataract surgery and/or cataract too advanced to grade).

RESULTS

Overall, 41% of the Barbados Eye Study population had any lens changes, including 3% with aphakia or an intraocular lens. Among the population of African descent, cortical opacities (34%) were most prevalent, followed by nuclear (19%) and posterior subcapsular (4%) opacities. Prevalence of all opacity types increased with age (P < .001). Cortical and nuclear opacities were more frequent in women than men. When prevalence of a single kind of opacity was considered, 21% of participants had cortical only, 6% had nuclear only, and 0.4% had posterior subcapsular only; 13% had mixed opacities. Visual acuity loss to worse than 20/40 in the more affected eye was present in 48%, 26%, and 18% of nuclear only, posterior subcapsular only, and cortical only types, respectively, and in 53% of mixed opacities.

CONCLUSIONS

The Barbados Eye Study provides the first prevalence data on different types of lens opacities in a large, predominantly black population. Whereas nuclear opacities are most common in white populations, cortical opacities were the most frequent type in the Barbados Eye Study, a finding of possible etiologic relevance. Other results highlight a higher frequency of opacities in women than men and a high prevalence of visual acuity loss in affected eyes.

Nine-Year Incidence of Open-Angle Glaucoma in the Barbados Eye Studies

PURPOSE

To determine the 9-year incidence of open-angle glaucoma (OAG) in African-descent participants of the Barbados Eye Studies.

DESIGN

Nine-year cohort study with 81% to 85% participation.

PARTICIPANTS

Three thousand two hundred twenty-two persons without definite OAG at baseline, at risk of developing OAG at follow-up.

METHODS

The standardized protocol included automated perimetry and various ophthalmic measurements, with a comprehensive ophthalmologic examination for those referred. Fundus photographs were evaluated independently by masked graders. Incidence was estimated by the product-limit approach. Relative risk (RR) ratios with 95% confidence intervals (CIs) were based on Cox regression models with discrete time.

MAIN OUTCOME MEASURE

Nine-year incidence of definite OAG, based on the development of visual field defects and glaucomatous optic neuropathy, with ophthalmologic confirmation.

RESULTS

The 9-year incidence of definite OAG was 4.4% (95% CI, 3.7%-5.2%), or an average of 0.5%/year, based on 125 new cases. Incidence increased greatly with age, from 2.2% at ages 40 to 49 years to 7.9% at ages 70 years or older, and tended to be higher in men than women (4.9% vs. 4.1%; RR, 1.3; 95% CI, 0.9-1.8). More than half (53%) of new cases were undetected, and of these, one third had intraocular pressure of 21 mmHg or less. When 141 persons developing suspected/probable OAG were considered, the total incidence was 9.4% (8.4%-10.6%), averaging approximately 1%/year, also increasing with age, and significantly higher in men than women (10.7% vs. 8.6%; RR, 1.31; 95% CI, 1.02-1.67).

CONCLUSIONS

These new data provide a measure of the long-term risk of OAG in an African-descent population, which is markedly higher than in persons of European ancestry. Results confirm the increased risk with age and in men. The incidence data fill a gap in our understanding of OAG risk and have implications for public health policy and planning; they also will allow the study of factors related to the risk of OAG development.

Foveal avascular zone in idiopathic juxtafoveolar telangiectasia

We measured angiographically the foveal avascular zone (FAZ) in 26 subjects with idiopathic juxtafoveolar telangiectasia (IJFT) and 27 control subjects. Quantitatively, FAZ was significantly smaller in IJFT (median = 0 mm2) than in controls (median = 0.405 mm2). Qualitatively, the telangiectasia in IJFT was temporal (92.5% of eyes) and appeared as microaneurysms interconnected with several capillaries, spider-shaped microaneurysms, or Coats'-like telangiectasia. IJFT is characterized by temporal telangiectasia and small FAZ.

Carbon dioxide laser therapy of recurrent squamous papilloma of the conjunctiva

Juvenile squamous papilloma of the conjunctiva may exhibit "malignant" behavior with multiple recurrences presenting difficulty in management. We have successfully treated a child with the carbon dioxide laser who had failed three previous surgical excisions, cryotherapy (twice), and chemotherapy. The carbon dioxide laser permits a precise form of tissue excision with minimal trauma, edema, and scarring, and offers a safe alternative approach to the management of these lesions.

Incidence of open-angle glaucoma: the Barbados Eye Studies. The Barbados Eye Studies Group

OBJECTIVE

To measure the 4-year risk of open-angle glaucoma (OAG) in a black population.

DESIGN

Population-based cohort study with 4 years of follow-up.

SETTING

Simple random sample of residents of Barbados, West Indies, aged 40 years or older.

PARTICIPANTS

A total of 3427 members of the cohort (85% of those eligible).

MAIN OUTCOME MEASURE

Development of glaucoma visual field defects and optic disc damage, confirmed by automated perimetry, independent fundus photographic gradings, and standardized ophthalmologic examinations.

RESULTS

The 4-year risk of OAG in black participants was 2.2% (95% confidence interval, 1.7%-2.8%), based on 67 newly developed cases of OAG. Incidence rates increased from 1.2% at ages 40 to 49 years to 4.2% at ages of 70 years or more, tending to be higher in men than women (2.7% vs 1.9%). About half of the incident cases were undiagnosed previously, and the rest were receiving OAG treatment. Of the 67 new cases of OAG, 32 had intraocular pressure of 21 mm Hg or less at baseline (1.2% incidence) and 35 had higher pressures (9% incidence). Risk was highest among persons classified as having suspect OAG at baseline (26.1%), followed by those with ocular hypertension (4.9%) and lowest in the remaining population (0.8%).

CONCLUSIONS

This longitudinal study provides new information on OAG risk, as well as the first incidence measurement in a black population. Although intraocular pressure increased risk, about half of the new cases had baseline pressures of 21 mm Hg or less. Results substantiate the high OAG risk in the population of African origin, especially in older adults; the relative role of intraocular pressure; and the considerable underdetection of new disease after 4 years of follow-up.