Strabismus and Near Point of Convergence and Amblyopia in 4–6 Year-Old Children

Abstract

Purpose: To determine the prevalence of strabismus and amblyopia, and the distribution of the near point of convergence (NPC), in a population of children aged 4 to 6 years. Methods: In this cross-sectional study, preschoolers in Mashhad were sampled using a random multistage cluster sampling approach. Examinations were done after obtaining parental consent. All participants had measurements of uncorrected visual acuity, corrected visual acuity, and non-cycloplegic refraction, and they had near and far cover tests to determine tropia and phoria. Results: Of the 3765 selected children, 3701 participated in the study. The prevalence of tropia was 1.21% (95% confidence interval [CI]: 0.86–1.57). Near and near/far tropia was observed in 0.83% (95% CI: 0.53–1.12) and 0.39% (95% CI: 0.18–0.59), respectively. Tropia was significantly more prevalent in boys (P=0.005). The most common type of tropia was esotropia, 0.22% (95% CI: 0.07–0.37). Among participants, 63.92% (95% CI: 62.36–65.48) had phoria; prevalence of far, near, and near/far phoria was 0.22% (95% CI: 0.07–0.37), 60.47% (95% CI: 58.88–62.07), and 3.22% (95% CI: 2.65–3.8), respectively. Mean NPC was 5.1 cm (95% CI: 5.05–5.14). NPC increased by 0.08 cm per month of age (P=0.033) and was 0.10 cm higher in boys compared to girls (P=0.027). Based on NPC, 61.58% (95% CI: 59.99–63.17) were symptomatic. The prevalence of amblyopia was 0.41% (95% CI: 0.20–0.61). The type of amblyopia was anisometropic, strabismic, and isoametropic in 75%, 11.1%, and 8.5%, respectively. Conclusion: The prevalence of amblyopia in this study population was not high; however, the prevalence of tropia was average compared to previous studies in Iran. Describing NPC in a 4- to 6-year-old Iranian population for the first time, we found that NPC increased with age in this sample.