Prevalence of Refractive Errors and Number Needed to Screen among Rural High School Children in Southern India: A Cross-sectional Study

Abstract

Introduction: Avoidable blindness is mainly due to uncorrected refractive errors (URE). School Eye Screening (SES) can be used as an initiative to address this issue. Aim: To determine prevalence of URE and Number Needed to Screen (NNS) to find one child with low vision or blindness from URE among rural school children. Materials and Methods: A cross-sectional study was performed in 22 government schools with sixth to ninth grades in Kaniyambadi block of Vellore District of Tamil Nadu, India. There were 4739 children on the rolls. Among children present, all those identified to have a visual deficit in either eye, using a single line 20/40 Snellen’s optotype E chart at 6 m, were referred to the hospital for confirmatory evaluation. Blindness (uncorrected) was defined as inability to see 20/200 in the better eye. In two of these schools, visual deficits were validated through a second school based examination by a clinician. Results: Of the 4739 children on rolls, 601 were absent; all 4138 (87.3%) who were present underwent screening; 2.3% (98) {95% Confidence Interval (CI) 1.8 to 2.8} failed the screening test in at least one eye and were referred for examination. Only 28 (28.6%) of 98 children who were referred came for examination to the hospital. In the 2 of the 22 schools where the visual deficit was validated, there were no false positives. The prevalence of refractive error in these two schools was 2.2% (95% CI 1.7 – 2.7). NNS to detect one child with low vision or blindness from URE was 147. Conclusion: Magnitude of refractive error, low NNS, low response to referral necessitates complete care at school and hence a relook at the current SES program.

Keywords

• avoidable blindness
• childhood blindness
• low vision
• myopia
• school eye screening