The Prevalence of Fusional Vergence Dysfunction in a Non-Selected Population in Iran

Purpose: The aim of this study was to determine the prevalence of fusional vergence dysfunction and its association with age, sex, accommodative amplitude and refractive errors in a non-selected population. Methods: This cross-sectional study is part of the Mashhad Eye Study (MES) which was conducted in Mashhad, northeast of Iran. The target population of Mashhad Eye Study was all Mashhad residents above 1 year of age. Random stratified cluster sampling was done to select participants and comprehensive examinations were performed for all participants including measurement of visual acuity, refraction, assessment of binocular vision and accommodative status, and slit lamp biomicroscopy. The age group 10-49 years was included in this report. Participants with strabismus, amblyopia, best corrected visual acuity less than 20/30 in either eye, history of ocular trauma and intraocular surgery and any systemic or ocular pathology were excluded from the study. Results: Of the 4453 invited individuals, 3132 participated in the study. After applying the inclusion and exclusion criteria, statistical analysis was performed on the data of 1683 participants. The prevalence of fusional vergence dysfunction was 3.24% (95%CI: 2.24-4.24) in all subjects, 4.02% (95%CI: 2.22-5.82) in men, and 2.89% (95%CI: 1.83-3.95) in women (p=0.219). The prevalence of fusional vergence dysfunction increased linearly with aging from 2.35% (95%CI: 1.00-3.70) in the age group 10-19 years to 5.45% (95%CI: 2.65-8.26) in the age group 40-49 years (p=0.034). According to the multiple logistic regression in the presence of age, sex, accommodative amplitude and spherical equivalent of refraction, only accommodative amplitude showed a significant association with fusional vergence dysfunction (odds ratio=0.87, 95C%:0.80-1.95, p<0.001). Conclusion: The prevalence of fusional vergence dysfunction in this study was higher than most previous reports and increased significantly with age-related decrease in accommodative amplitude. Fusional vergence dysfunction had no significant association with sex and refractive errors.