Prevalence of convergence insufficiency among Spanish school children aged 6 to 14 years

Clinical relevance: Convergence insufficiency (CI) at an early age can lead to learning difficulties affecting school performance. The aim of this study was to examine the prevalence of CI in a non-clinical population of Spanish children using well defined clinical criteria and to determine whether sex is a risk factor. Methods: Visual acuity and binocular vision tests were performed in 628 children aged 6-14 years (mean age 9.6 +/- 1.3 years) at three schools in the Madrid Community, Spain. To assess CI prevalence we used CITT (Convergence Insufficiency Treatment Trial) criteria. The three signs considered were: i) exophoria at least 4(Delta) greater at near than at far; ii) near break point of convergence (NPC) >= 6 cm; and iii) reduced positive fusional vergence (PFV) at near (<= 15(Delta) base-out break or failed Sheard's criterion). Results: The CI prevalence detected was 5.30% (33 children). Proportions of children with one or two signs of CI were 23.76% (148 children) and 12.20% (76 children), respectively. No differences in these CI rates by sex were detected. Conclusion: The clinically significant CI prevalence observed here suggests the need for more binocular vision screening programmes in school settings. (C) 2021 Spanish General Council of Optometry. Published by Elsevier Espana, S.L.U. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).