Clinical features and treatment of near-work-related acquired esotropia.

Aim: To investigate the characteristics of near-work-related esotropia and the clinical efficacy of botulinum toxin type A (BTXA) injection therapy on it.

Methods: A total of 107 patients aged 15-57y with near-work-related esotropia were taken as the BTXA-treated group, and 30 other peers without near-work-related esotropia were included in the control group. All participants were refractive corrected to analyse the clinical characteristics of near-work-related esotropia. All subjects were examined including Worth4 spot examination, stereoscopic vision, strabismus angle, accommodative convergence to accommodation ratio (AC/A), far and near positive and negative convergence, positive and negative fusion range, positive and negative relative accommodation. Clinical efficacy was evaluated at a period of 10mo follow-up.

Results: The distant and near stereopsis were found in 84.9% and 77.5% of patients in the BTXA-treated group, respectively. In the control group, all patients had distant and near stereopsis. The incidence of taking off one's glasses to see close objects was significantly higher in the BTXA-treated group than in the control group (<0.05). The BTXA-treated group showed a smaller range of in-fusion (9.84±5.72)° than the control group (22.04±8.71)° (<0.05). The near esotropia angle of the BTXA-treated group (17.08±11.98) was significantly smaller than the distant esotropia angle (19.07±11.68) (<0.05). Ten months after injection, the diplopia and esotropia of most patients underwent improvements after treatment (<0.05).

Conclusion: This study reveals that the accommodation function and the habit of near work without wearing spectacles are associated with near-work-related esotropia, while the length of time for near work and the onset time are independent of near-work-related esotropia. Additionally, BTXA injection therapy plays a vital role in relieving diplopia and restoring eye position.