Prevalence of visual impairment and refractive error in school-aged children in South Darfur State of Sudan

Background: Global estimates suggest there are almost 19 million visually impaired children worldwide, the major cause being uncorrected refractive error (RE).Aim: To assess the prevalence of visual impairment (VI) and RE among Sudanese school-aged children.Setting: Eight randomly selected primary schools from 21 districts in South Darfur State of Sudan were involved.Methods: A school-based cross-sectional study of RE and VI in primary schoolchildren from grades 1 to 8 (children aged 6–15 years) was investigated. A Refractive Error Study in Children (RESC) protocol was implemented to determine the prevalence of RE and VI in these schoolaged children. Participants were enrolled through stratified multistage cluster sampling of four all-male and four all-female primary schools from South Darfur State of Sudan. Examination procedures followed the RESC protocol, which included visual acuity (VA) measurements, binocular vision assessments, retinoscopy and autorefraction under cycloplegia, as well as examination of the external eye, anterior-segment, media and fundus.Results: A total of 1775 children were invited to participate in the study and 1678 were examined resulting in a participation rate of 94.5%. The findings indicated that the prevalence of uncorrected, presenting and best-corrected VA of 6/12 or worse was 6.4% (95% confidence interval [CI], 4.9–7.9), 4.4% (95% CI, 2.9–5.9) and 1.2% (95% CI, 0.3–2.7) respectively. RE was the cause of VI in 57% of participants, retinal disorders in 13.1%, amblyopia in 5.6%, corneal opacity in 0.9%, cataract in 3.7%, with the causes of reduced vision undetermined in 10.3% and various other causes contributed 9.3%. External and anterior-segment abnormalities were observed in 10.2% of children. This was mainly allergic conjunctivitis (5.3%) followed by bacterial and viral conjunctivitis (4.2%). The prevalence of myopia (≥|-0.50 D|) in one or both eyes was 6.8% (95% CI, 5.3–8.3), hypermetropia (≥ 2 D) was noted in 1.9% (95% CI, 0.4–3.4) and astigmatism (≥|-0.75 D|) prevailed in 2.5% (95% CI, 1.0–4.0). Prevalence of VI among schoolaged children were associated with the children’s age and grade levels (p = 0.00) but was not correlated with gender (p = 0.224). Prevalence of RE among school-aged children was significantly correlated with age and grade levels (p = 0.00). No significant correlation was found between gender and prevalence of RE (p = 0.833). The prevalence of VI because of myopia was associated with increasing gra