Epidemiology of non-strabismic binocular vision anomalies in Africa: a systematic review and meta-analysis.

Abstract

Clinical relevance: Non-strabismic binocular vision anomalies (NSBVAs) are common causes of visual discomfort and reduced visual efficiency. Understanding their prevalence in African populations is essential for informing routine binocular vision assessment and improving clinical decision-making in optometric practice across the continent.

Background: NSBVAs contribute significantly to asthenopic symptoms and functional visual problems, yet their epidemiology in Africa has not been systematically synthesised. This review aimed to estimate the pooled prevalence of NSBVAs in Africa and to examine the diagnostic criteria used across studies.

Methods: A systematic review and meta-analysis were conducted in accordance with PRISMA guidelines. Studies reporting the prevalence of NSBVAs in African populations were searched from database inception to 12 December 2025 in Scopus, PubMed, Web of Science, and Ovid MEDLINE. Risk of bias was assessed using the Joanna Briggs Institute Critical Appraisal Tool for prevalence studies. Random-effects meta-analyses were performed in R to calculate pooled prevalence estimates, and heterogeneity was assessed using the I² statistic. The review protocol was prospectively registered with PROSPERO (CRD42025648345).

Results: Nine studies from Ghana, Nigeria, and South Africa, including 2,932 participants, met the inclusion criteria. The pooled prevalence of vergence anomalies was 19.19% (95% CI: 13.36-26.80%; six studies), with convergence insufficiency being the most prevalent (9.20%; 95% CI: 4.47-18.00%). The pooled prevalence of accommodative anomalies was 18.87% (95% CI: 17.27-20.59%; five studies), with accommodative infacility being the most common (9.00%; 95% CI: 5.97-13.35%).

Conclusion: Across the included studies, approximately one in five participants met study-specific criteria for accommodative or vergence anomalies. However, because diagnostic criteria and symptom requirements varied and the certainty of evidence was very low, these estimates should be interpreted as indicative rather than definitive population prevalence estimates. These findings highlight the need for routine binocular vision assessment, standardised diagnostic criteria, and expanded epidemiological research to support evidence-based optometric care in Africa.