Severity-dependent Disruption of Binocular Accommodative Amplitude And Near Fusional Reserves in Children with Hyperopic Anisometropia

To investigate whether increasing severity of anisometropia is associated with progressive disruption of binocular accommodative amplitude (AMP), reduced near fusional reserves and near point of convergence (NPC) in children.

This prospective cross-sectional study included 59 hyperopic children aged 5–10 years. Participants were classified into three groups according to cycloplegic interocular spherical equivalent refraction (SER) difference: normal control (NC, n = 13, SER difference < 0.50 D), mild anisometropia (MA, n = 30, SER difference ≥ 0.50 and <3.00 D) and severe anisometropia (SA, n = 16, SER difference ≥ 3.00 D). Both untreated amblyopic and non-amblyopic children were included in the anisometropic groups. AMP was measured using the minus-lens method with full refractive correction. Interocular accommodative asymmetry was calculated as the absolute difference in AMP between eyes. Near fusional vergence reserves at a standard near working distance of ~40 cm and NPC were assessed under binocular viewing conditions. Group comparisons, partial correlation analyses controlling for age and sex and linear regression analyses were performed.

Compared with the NC group, children with anisometropia demonstrated significantly reduced AMP, increased interocular accommodative asymmetry and diminished near base-out (BO) fusional vergences, particularly in the SA group (all p < 0.05). Increasing interocular SER difference was significantly associated with reduced nondominant eye AMP (r = −0.46), greater interocular AMP asymmetry (r = 0.29) and reduced near BO fusional vergence break and recovery points (r = −0.49 and −0.43, respectively). Regression analysis showed that the interocular SER difference accounted for up to 31.6% of the variance in near BO fusional vergence reserves.

Greater anisometropia in children is associated with dose-dependent disruption of interocular AMP and selective reduction of convergent fusional reserves. These findings suggest anisometropia contributes to binocular motor dysfunction beyond sensory imbalance, highlighting the importance of comprehensive binocular function assessment in anisometropic children.

ChiCTR2500103539, date of registration: 2025-05-30.