Prevalence of vision impairment and refractive error in school learners in Calabar, Nigeria

Background: Uncorrected refractive error could negatively affect learning and academic performance, there is still inadequate information for planning school health. Aim: To determine the proportion of students with vision impairment because of uncorrected refractive error, and prevalent types among learners aged 10-18 years. Setting: The study site included two of 18 local government areas of the Cross River State in Nigeria, with 23 public and mission secondary schools. Methods: A two-stage cluster sampling method was used to enrol 4241 study participants from eight selected secondary schools. Results: The prevalence of vision impairment (presenting visual acuity worse than 6/12) was 7.9% (95% confidence interval [CI]: 7.17% - 8.6%). The prevalence of vision impairment because of refractive error was 7.2% (95% CI: 6.41% - 7.96%) in the better eye. Astigmatism was the predominant type of refractive error with a prevalence of 4.2% (95% CI: 3.6% - 4.8%), followed by myopia (1.72%; 95% CI: 1.3% - 2.1%) and hyperopia (1.3%; 95% CI: 0.9% - 1.6%). There were statistically significant differences in proportions of female participants who presented with myopic astigmatism (30.8%; p < 0.012). Statistically significant difference in proportions was found in older (33.3%; p < 0.0004) and male (29.6%; p < 0.0003) participants who presented with hyperopic astigmatism compared to younger and female participants, respectively. Myopia accounted for 4.8% (95% CI: 4.2%- 5.5%) and was significantly higher in female participants (5.5%; p < 0.033). Conclusion: Refractive error was the major cause of vision impairment and myopic astigmatism was the predominant type of refractive error among secondary school children in Calabar.