Botulinum toxin type A in treating early-stage patients with small-angle acute acquired comitant esotropia.

[AIM] To investigate botulinum toxin A (BTXA) efficacy on small-angle (≤25) acute acquired concomitant esotropia (AACE) in early-stage patients.

[METHODS] The electronic medical record data of AACE patients during March 2019 and June 2023 were collected in this retrospective and hospital-based cohort study. A total of 72 small-angle AACE patients received BTXA extraocular muscle injection. Patients were grouped by onset-to-treatment time (Group A: ≤6mo, Group B: >6mo). Deviation of esotropia, eye alignment and stereopsis were analyzed at the period of pre/post-injection (1wk, 1, 3, and 6mo). Orthophoria rate at 6mo (horizontal deviation <10 and binocular single vision) were considered as outcome index.

[RESULTS] There were no significant baseline differences (>0.05) between two groups except onset-to-treatment time (2mo 11mo, <0.001). Higher orthophoria rates were in Group A at last follow-up (94.74% 73.53%, =0.013). Post-BTXA deviations of two groups at 1mo showed no difference (>0.05); while in 3 and 6mo Group A was significantly smaller than group B (all <0.001). No statistically significant differences were observed among all post-BTXA deviations of near and distance in Group A. In Group B, deviation at 3mo (near: 2 0, <0.001; distance: 4 0, <0.001) and 6mo (near: 6 0, <0.001; distance: 6 0, <0.001) was significant increased compared to deviation at 1wk after treatment. Group A showed better stereopsis recovery in last follow-up compared to Group B (80″ 200″, =0.002). Both groups obtained improved stereopsis after treatment (Group A: 80″ 300″, <0.001; Group B: 200″ 300″, =0.037).

[CONCLUSION] BTXA is effective for AACE with small deviation (≤25) in early stage. Delayed treatment (>6mo) may reduce BTXA efficacy. Early BTXA intervention benefits long-term eye alignment and stereopsis recovery.