Progressive binocular visual alterations associated with increasing myopic anisometropia in spectacle-corrected...

To characterize the severity-dependent pattern of accommodative and binocular visual alterations in spectacle-corrected children with myopic anisometropia, normal best-corrected visual acuity (BCVA), and no clinically significant binocular vision-related symptoms.

This hospital-based cross-sectional study included 153 myopic anisometropic and 104 myopic isometropic children. Cycloplegic refraction, axial length, ocular dominance, accommodative function, fusional vergence, heterophoria, Worth Four-Dot Test responses, and stereoacuity were assessed. All binocular vision examinations were performed under full spectacle correction. Anisometropia severity was quantified using vector dioptric distance (VDD). Multivariable regression models were used to evaluate associations between VDD and selected accommodative and binocular visual outcomes.

With increasing anisometropia severity, amplitude of accommodation in the nondominant eye decreased from 10.73 ± 3.10 D in the mild group to 9.05 ± 3.12 D in the high group (p-trend = 0.007), and accommodative facility decreased from 8.3 ± 4.4 to 5.5 ± 4.4 cpm (p-trend = 0.005). Interocular accommodative imbalance increased progressively. The prevalence of clinically meaningful near esophoria increased from 5.9% to 33.3% (p-trend = 0.009) and reduced near base-in vergence increased from 10.2% to 42.9% (p-trend = 0.001). Near Worth Four-Dot diplopia increased from 13.7% to 28.0% (p-trend = 0.05). Near stereoacuity worsened progressively across severity strata (p-trend < 0.001). After adjustment for age, binocular mean spherical equivalent, and relevant binocular covariates, increasing VDD remained independently associated with greater interocular accommodative imbalance, reduced near base-in vergence, a higher likelihood of diplopia on the near Worth Four-Dot Test, a more esophoric near phoria value, and poorer near stereoacuity.

Increasing myopic anisometropia was associated with a severity-dependent pattern of subclinical alterations in accommodative balance, ocular alignment, fusional vergence, sensory fusion, and stereoacuity in spectacle-corrected children with normal BCVA. These findings support a multifactorial interpretation involving accommodative, optical, vergence, and sensory factors; however, their relative contributions and causal sequence cannot be determined from this cross-sectional study. Longitudinal and interventional studies are needed to clarify the mechanisms and clinical significance of these alterations.