Prevalence of glaucoma in a rural east African population
Purpose: To determine the prevalence of glaucoma in an adult population in rural central Tanzania.
Methods: Six villages were randomly selected from eligible villages in the Kongwa district, and all residents more than 40 years of age were enumerated and invited to a comprehensive eye examination including presenting visual acuity, refraction, automated 40-point Dicon (San Diego, CA) suprathreshold screening field test, Tono-Pen (Bio-Rad, Inc., Boston, MA) intraocular pressure (IOP) measurement, and standardized examination by an ophthalmologist of anterior segment, optic nerve head, and retina after pupil dilation. Gonioscopy and Glaucoma-Scope (Ophthalmic Imaging Systems, Sacramento, CA) optic disc imaging were performed on those with IOP higher than 23 mm Hg and cup-to-disc ratio (c/d) more than 0.6 and on a 20% random sample of participants.
Results: Of 3641 eligible persons, 3268 (90%) underwent ophthalmic examination. The prevalence of glaucoma of all types was 4.16% (95% confidence interval [CI] = 3.5, 4.9%). Primary open-angle glaucoma (OAG) was diagnosed in 3.1% (95% CI = 2.5, 3.8%), primary angle-closure glaucoma (ACG) in 0.59% (95% CI= 0.35, 0.91%), and other forms of glaucoma in 0.49%. The prevalence of glaucoma was found to be sensitive to changes in the diagnostic criteria.
Conclusions: The high prevalence of OAG in this group was similar so that of African-derived persons in the United States but less than in African-Caribbean populations. ACG was more prevalent in east Africans than suggested by anecdotal reports.
Published courtesy of: Invest Ophthalmol Vis Sci. 2000; 41: 40-48
Patterns of open-angle glaucoma in the Barbados family study
Objective: To describe the Barbados Family Study of open-angle glaucoma (OAG) and present risk factors for OAG in siblings of study probands.*
Design: Observational study of families of probands with OAG.
Participants: Two hundred thirty probands and 1056 relatives (from 207 families).
Methods: Probands and their family members underwent standardized examinations, including automated perimetry, applanation tonometry, ophthalmologic evaluation, fundus photography, blood pressure, interview, and genotyping. Generalized estimation equation methods were used to evaluate risk factors in the siblings, including demographic, medical and ocular characteristics.
Main Outcome Measures: Presence of OAG in the relatives, as defined by both visual field and optic disc findings, after ophthalmologic exclusion of other causes.
Results: The median ages of probands and relatives were 68 and 47 years, respectively. In the 207 families, 29% of the probands had one relative with OAG and 10% had two or more relatives affected. Of the 1056 family members, 10% had OAG, 13% had suspect OAG, and 6% had ocular hypertension. One fifth of the 338 siblings had OAG (n = 67); they tended to be older and more often were male. Multivariate comparisons between siblings with and without OAG found that age, higher intraocular pressure (IOP), myopia, and lower diastolic blood pressure – IOP differences were related to OAG, whereas hypertension and diabetes were not.
Conclusions: Based on standardized protocols and examinations, approximately one quarter of the relatives had OAG or suspected OAG, despite their relatively young age. Risk factors for OAG in siblings were similar to risk factors in unrelated individuals. Although definitive conclusions about the extent of OAG among the relatives are not possible at this time given their relatively young age, a future follow-up of these individuals may yield additional information on the genetic transmission of OAG. Analyses are ongoing to determine OAG inheritance and to localize potential gene(s) involved.
Published courtesy of: Ophthalmology 2001; 108: 1015-1022
* Proband – a person with, e.g., a physical disorder, who is a ‘starting point’ for a genetic study – Editor
Evaluation of a national eye care programme: re-survey after 10 years
Aim: To re-survey the Gambia after an interval of 10 years to assess the impact of a national eye care programme (NECP) on the prevalence of blindness and low vision.
Methods: Comparison of two multistage cluster random sample surveys taking into account the marked increase in population in the Gambia, west Africa. Samples of the whole population in 1986 and 1996 were taken. The definition of blindness is presenting vision less than 3/60 in the better eye, or visual fields constricted to less than 10 from fixation. Low vision is less than 6/18 but 3/60 or better. Causes of blindness were determined clinically by three ophthalmologists.
Results: The crude prevalence of blindness fell from 0.70% to 0.42%, a relative reduction of 40%. During the same 10 year period, the population increased by 51% from 775,000 to 1,169,000. When the results were standardised for age, a west to east gradient was found for changes in risk of blindness over the 10 year period. This matched the phased west to east introduction of the NECP interventions. There was a modest but significant increase in the risk of low vision across the whole country.
Conclusions: The overall reduction in risk of blindness, in those areas where the NECP has been active, appears to justify the programme and the support of donor organisations. The low vision cases due to cataract must now be addressed.
Published courtesy of : Br J Ophthalmol 2000; 84: 948-951