title: Prevalence and risk factors for lens opacities in Nigeria: results of the national blindness and low vision survey.
abstract: OBJECTIVE
  Investigate prevalence and risk factors for lens opacities among a nationally representative sample of Nigerians aged ≥ 40 years.
  
  
  METHODS
  Across 305 clusters, 13,591 adults were examined. Every seventh participant (n = 1722) was sampled systematically and examined in detail, including lens opacity grading. Lenses were examined at the slit-lamp with pupil dilation and graded using the World Health Organization (WHO) system. Significant opacities were defined as nuclear, cortical, or posterior subcapsular opacity of WHO grade >1, or hyper/mature cataract. The category "Any Opacity" included hyper/mature opacity and aphakia/pseudophakia/couching. Data were collected on sociodemographic and environmental factors, including height and weight.
  
  
  RESULTS
  A total of 1631/1722 (95%) in the normative subsample had their lenses graded. Prevalence of "Any Opacity" was 19.8% (95% confidence interval [CI]: 7.9-21.7) the prevalence of all types increased with age, and was higher in females and those not literate. Prevalence of nuclear, cortical, and posterior subcapsular were 8.8% (95% CI: 7.5-10.1); 11.7% (95% CI: 10.0-13.3); and 2.9% (95% CI: 2.1-3.8), respectively. In multivariate analysis, age was an independent risk factor for all types. Nuclear opacity was also associated with female sex (odds ratio [OR] 2.4; 95% CI: 1.5-3.6); lean body mass index (BMI; OR 2.0; 95% CI: 1.1-3.5); and the Igbo ethnic group (OR 4.4; 95% CI: 2.3-8.4). Cortical opacity was also associated with female sex (OR 2.1; 95% CI: 1.5-3.0) and the Yoruba (OR 0.45; 95% CI: 0.3-0.8), but not with BMI. "Other Lens Opacities," which includes couching, was significantly lower in the Guinea savannah region (OR 0.4; 95% CI: 0.2-0.9), while living in rain forest areas was protective for posterior subcapsular cataracts (OR 0.3; 95% CI: 0.1-0.7).
  
  
  CONCLUSIONS
  A fifth of Nigerian adults have some degree of lens opacity. Further studies are needed to investigate the role of ethnicity, climate variables, and other risk factors.
authors: Abubakar Tafawa Balewa University Teaching Hospital, Bauchi, Nigeria.
authors: Abdull M
authors: AM
authors: Mahdi
authors: Mansur
authors: M
authors: Rabiu
authors: Clare
authors: C
authors: Gilbert
authors: Selvaraj
authors: S
authors: Sivasubramaniam
authors: Gudlavalleti V S
authors: GV
authors: Murthy
authors: Christian
authors: C
authors: Ezelum
authors: Gabriel
authors: G
authors: Entekume
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001766:Blindness / Q000453:epidemiology* / Q000209:etiology; D002386:Cataract / Q000150:complications / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009549:Nigeria / Q000453:epidemiology; D011159:Population Surveillance; D015995:Prevalence; D012307:Risk Factors; D015354:Vision, Low / Q000453:epidemiology* / Q000209:etiology; D014792:Visual Acuity
keywords: Nigeria; cataract risk factors; epidemiology; lens opacities; prevalence