Abstract:  Objective To observe the efficacy of botulinum toxin type A (BTXA) injections transconjunctivally into the medial recti muscles on the patients with congenital esotropia. Design Retrospective case series. Participants 12 patients（24 eyes）with congenital esotropia diagnosed at the age of 6~34 months（mean 19.69±8.61 months）. Methods Visual acuity, slitlamp, fundoscopy and cycloplegic refraction were examed. Near (33 cm) and far (6 m) horizontal deviation (in both prism degree and degrees) determined using the simultaneous prism and cover test. When cooperation was not possible, we used Hirschberg's or Krimsky's method. Concurrent bilateral medial rectus muscle BTXA injections (2.5 u) monitored with electromyographic recording under sedation-anesthesia were used for all the patients. Patients were followed regularly at 2 weeks, 3 months, 6 months, 1 year and 2 years till last visit. Far deviation ≤10△ was considered as orthophoria. During follow up,  if deviation≥ 20△ and persist over 3 months, second injection will be given. Deviation and stereoscopic vision were recorded. Main Outcome Measures Best-corrected monocular visual acuity, refraction, deviation and stereoscopic vision. Results The diopter of the 12 patients was +0.375~+3.625 D（mean 1.88±0.84 D）. Patients were followed up for 4 to 84 months (mean 25.83±13.13 M) after the last injection. 8 patients required once bilateral injection and 4 patients required twice bilateral injections to achieve a favorable outcome. During follow-up, success rate of  BTXA injection was 83.33% (10/12 cases) . One case underwent standard surgery with recession of the medial rectus and resection of the lateral rectus muscle at the 14th month after the injection, who achieved after surgery. The other one case received prism diopters after injection since the deiviation decreased to +15△. Till last visit all patients achived orthophoria after combined  treatment. 4 cases achieved gross stereopsis. Conclusion BTXA injection transconjunctivally into the medial recti muscles is an effective treatment modality for the management of congenital esotropia in infants and children. It can be injected repeatly 3 months later.

Key words: congenital esotropia/drug therapy, botulinum toxin type A