Fusional Vergence

Body Mass Index (BMI) is a common indicator of nutritional and general health, but its possible effect on visual performance, especially binocular vision, has not been widely studied. This study investigated how BMI influences binocular vision parameters Near Point of Convergence (NPC) , Amplitude of Accommodation (AoA) , Heterophoria, and Fusional Vergence among healthy young adults. A descriptive cross-sectional study was conducted at the University of Benin Optometry Clinic involving 100 participants aged 17–30 years. Participants were grouped as underweight, normal, overweight, or obese based on the World Health Organization (WHO) BMI classification. NPC was measured with a meter rule, AoA using Donder’s push-up method, and both Heterophoria and Fusional Vergence assessed with a phoropter via the von Graefe technique. Data were analyzed using descriptive statistics and Pearson’s correlation at a 0.05 significance level. Results: BMI was significantly associated with NPC recovery (p = 0.047) but not NPC break (p = 0.121). AoA and Heterophoria showed no significant correlations with BMI (p = 0.529; p = 0.154/0.999). Negative Fusional Vergence (NFV) break at 6 m differed significantly across BMI groups (p = 0.043), whereas Decompensated Phoria did not (p = 0.249). BMI also showed a significant relationship with refractive status (p = 0.039),Over weight subject were more of myopic astigmatism and Obese Subject tended towards hyperopic astigmatism. Conclusion: Higher BMI appears to reduce convergence recovery and fusional divergence efficiency, though accommodation and heterophoria remain unaffected. This suggests that excess body weight may compromise oculomotor control through systemic or neuromuscular mechanisms. Incorporating BMI assessment into binocular vision evaluations is recommended to promote both ocular and general health.