Unilateral visual impairment: impact on binocular function of school children in rural communities of Saki-East, Southwest Nigeria

Abstract

This study was designed to determine the impact of unilateral visual impairment or blindness on binocular visual function in children. A multistage, cross-sectional study was conducted among primary and secondary school students in the Saki-East Local Government Area of Oyo State between May and July 2021. Unilateral visual impairment was defined as presenting visual acuity <+0.3 LogMAR. Stereopsis, contrast sensitivity and peripheral visual fields were assessed with the Titmus fly test chart, Mars Contrast sensitivity chart and Lister perimeter respectively. Chi-squared test and Logistic regression were performed to assess the association between the degree of unilateral visual impairment and the other independent variables. Fifty-one of 3671 (1.4%) children had unilateral visual impairment or blindness. The mean age was 10.7 ± 3.6 years. Stereopsis was weak or absent in 38 (74.5%) participants, contrast sensitivity values were impaired in 50 (98%) participants, and 29 (61.7%) participants had constricted peripheral visual fields. The level of stereopsis of participants worsened with increasing severity of the unilateral visual impairment, and this was statistically significant (p < 0.001). Children with unilateral visual impairment had poor binocular function. This correlated with stereopsis, worse in participants with severe visual impairment.