Is there an association between convergence insufficiency and refractive errors?

Abstract

Background: Refractive errors and convergence insufficiency play major roles in reading efficiency. Uncorrected refractive errors are a primary cause of binocular anomalies, including convergence insufficiency. Symptoms of asthenopia in both refractive and binocular vision anomalies are similar. Despite the relationships that exist between them, the extent of association between refractive errors and convergence insufficiency has not been studied extensively.Aim: The aim of this study was to determine the prevalence of convergence insufficiency and refractive errors and investigate their associations with gender and age in a sample of high school children.Methods: The study design was cross-sectional and comprised data from 1056 African high school students aged 13–18 years, who were randomly selected from 13 high schools in uMhlathuze municipality in the province of KwaZulu-Natal, South Africa. In the final sample, 403 (38%) were males and 653 (62%) were females. The participants’ mean age and standard deviation were 15.89 ± 1.58 years and median age was 16 years. Refractive errors, heterophoria, near point of convergence, fusional vergences and accommodative functions were evaluated.Results: Prevalences for convergence insufficiency were as follows: low suspect 12.4% (confidence interval, [CI] 10.2–14.4), high suspect 6.3% (CI, 5.0–7.9), definite 4.6% (CI, 3.4–5.9), and pseudo-convergence insufficiency 2.1% (CI, 1.2–3.0). Refractive errors were: hyperopia 6.8% (CI, 5.3–8.4), myopia 6.0% (CI, 4.6–7.5), astigmatism 2.3% (CI, 1.8–3.2), anisometropia 1.3% (CI, 0.7–2.0) and emmetropia 86.2% (CI, 85.1–89.1). There were no significant associations between convergence insufficiency and gender (p = 0.32), age (p = 0.38), grade levels (p = 0.99) or refractive errors (p = 0.08).Conclusion: The prevalence of clinically significant convergence insufficiency and refractive errors was low in this sample of black high school students in South Africa, and there was no significant correlation between them.