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Fatima Kyari, Clare Gilbert, Tunde Peto, Nigeria National and Visual Impairment Study Group; Risk Factors for Primary Open-Angle Glaucoma in Nigeria: Results of the Nigeria National Survey of Blindness and Visual Impairment. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4299.
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To explore risk factors for primary open-angle glaucoma (POAG) among adults aged ≥40 years in Nigeria. The glaucoma-specific blindness prevalence in Nigeria (0.7%, 95%CI 0.55-0.88%) among those aged ≥40 years is one of the highest ever reported.
Population-based survey of a nationally representative sample. 13,591 participants aged >40 years had logMAR visual acuity (VA) measurement, FDT visual field testing, autorefraction, A-scan biometry and optic disc assessment. Values for defining glaucoma using ISGEO levels of evidence i.e. vertical cup:disc ratio (VCDR), disc asymmetry and intraocular pressure (IOP) were derived from a systematically sampled normative subset of 1 in 7 participants. All in the normative sample and participants with VA <20/40 or suspicious optic discs had detailed examination including slit-lamp ocular biomicroscopy, Goldmann applanation tonometry, Van Herick’s angle estimation, gonioscopy, dilated funduscopy and fundus photography. Disc images were graded by Moorfields Eye Hospital Reading Centre. Glaucoma defining values were applied to the whole sample to identify participants with POAG. The following sociodemographic, systemic and ocular factors were assessed in univariate and multivariate analyses, taking account of the cluster design: age, gender, ethnic group and literacy; urban/rural residence; hypertension, blood glucose and body mass index (BMI); IOP, axial length and mean ocular perfusion pressure (MOPP), using standard/published definitions and categories.
96% of 13,591 participants had data on VCDR in at least one eye. 462 participants were classified as cases of POAG according to ISGEO’s 3 levels of evidence; with open angles. In univariate analyses the following were associated with POAG: increasing age, male gender, Ibo and Ijaw ethnic groups, being illiterate, longer ocular axial length, higher IOP, lower MOPP, any hypertension and greater severity of hypertension, low BMI and being underweight. In mutlivariate analysis, increasing age and higher IOPs were the only independent risk factors for POAG.
Risk factors for POAG in Nigeria are similar to those reported in other black populations in Africa and USA. This large, national survey does not identify subgroups of the population at significantly higher risk of POAG, which limits focused public health approaches for early detection.
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