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Fatima Kyari, Mohammed M. Abdull, Gudlavalleti V. Murthy, Clare Gilbert, Nigeria National Blindness and Visual Impairment Study Group; Ethnic Variations in the Prevalence of Glaucoma: Preliminary Results of the Nigeria National Survey on Blindness and Visual Impairment. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5321.
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© ARVO (1962-2015); The Authors (2016-present)
To determine ethnic variation in the prevalence of glaucoma among adults aged 40 years and older in Nigeria.
Multistage stratified cluster random sampling with probability proportional to size procedures were used to select a nationally representative sample of 15,027 persons aged 40 years and older across Nigeria. Systematic sampling of 1 in 7 of those examined (n=13,599) gave a subsample of 1,759 who were all examined in detail to construct a normative database. This subset was used to determine the normal values for cup:disc ratio (CDR) and intra-ocular pressure in the population. Glaucoma was diagnosed according to the ISGEO criteria. Presenting and best-corrected visual acuities (VA) were tested using a reduced logMAR E chart. Participants were asked about a history of glaucoma and their ethnicity. Detailed eye examination, in participants with VA worse than 20/40 in either eye or suspicious discs, included visual field testing with the FDT, autorefraction, dilated funduscopy and fundus photography. All images were graded by Moorfields Eye Hospital Reading Centre. Nineteen ethnic groups with 100 or more participants were identified.
Of the 6395 participants that required fundus photography, 3814 (59.6%) had images for CDR assessment in both eyes and 817 (12.8%) in at least one eye. Where there was no disc image, clinical CDR grades were used. Of the total 13,591 participants, there was no CDR grading in both eyes of 436 (6.8%) participants. The overall crude prevalence of glaucoma in Nigeria was 3.7% (95% CI 3.4-4.0%). The Ikwere ethnic group had the highest prevalence (6.1%, 95%CI 1.3-11.0%) followed by the Ibo (5.7%, 95%CI 4.7-6.8%). The lowest prevalence was amongst the Tiv (1.8%, 95%CI 0.4-3.2%). There is a need for adjudication in 34 (0.3%) and relevant data for glaucoma diagnosis was missing in 49 (0.4%) participants.
The prevalence of glaucoma in Nigeria is similar to earlier reports for glaucoma in the black population. However, this study demonstrates that there are considerable inter-ethnic variations even among black populations. Services needed for glaucoma care need to be targeted to populations at risk.
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