Vergence Profile and Prevalance of Non-Strabismic Vergence Anomalies Among School Children in Abia State, Nigeria

Purpose: To determine the prevalence of non-strabismic vergence anomalies and their relationship with age, gender, and school level in children aged 10-16 years Method: A cross-sectional study was conducted among 537 children (255 male, 282 females; mean age 13.0 +/- 2.0, years) selected from nine schools using stratified, cluster, and random sampling. The participants completed a Convergence Insufficiency Symptom Survey (CISS) and eye examinations, including the measurement of visual acuity, non-cycloplegic refraction, cover test, near point of convergence, fusional vergences, accommodative functions, and ocular health evaluation. All binocular tests were performed following the subjective refraction with the corrective lenses in place, if prescribed. Results: The prevalence of low suspect, high suspect, and definite convergence insufficiency was 9.6%, 5.8%, and 4.1%, respectively. Other prevalence estimates included convergence excess (2.9%), fusional vergence dysfunction (2.6%), basic exophoria (1.7%), basic esophoria (2.8%), divergence insufficiency (0.8%), and divergence excess (0.6%). The prevalence of high suspect (p < 0.01) and definite (p < 0.01) convergence insufficiency was significantly higher in older than younger children, and as expected, in secondary more so than primary school children (p = 0.01). There was no statically significant association between gender and various vergence anomalies. Conclusion: The study showed that vergence anomalies are common vision conditions among Abia State school children. Given the importance of visual skills in learning and academic achievements, there is a need to develop screening and management strategies that will target those visual conditions to prevent educational and social progress being affected.