Botulinum toxin for the treatment of strabismus

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 (≤25Δ) 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 <10Δ and binocular single vision) were considered as outcome index.

RESULTS

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

CONCLUSION

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

Botulinum Toxin A Injection in Horizontal Nystagmus: Effect on the Frequency of the Oscillation on a Pediatric Population

PURPOSE

To evaluate the effect of botulinum toxin A injection on the frequency of horizontal nystagmus in children.

METHODS

This was a non-randomized before-and-after clinical trial evaluating a cohort of children with horizontal nystagmus before and after treatment with botulinum toxin A. The toxin was injected under general anesthesia with spontaneous ventilation without intubation using the Mendonça forceps and the effect was evaluated by analyzing the frequency of the oscillation in Hertz (Hz) on video registrations before and after treatment.

RESULTS

The current study found a statistically significant difference on the frequency of the nystagmus in children before and after the injection of botulinum toxin A, with the mean frequency decreasing from 1.55 ± 0.94 Hz before treatment to 1.04 ± 0.87 Hz at 1 month post-injection (P < .001) and to 1.27 ± 0.87 Hz at 6 months post-injection (P = .002). When comparing the data 1 and 6 months post-injection, this study found a significant increase (P = .001) in the frequency of the nystagmus.

CONCLUSIONS

The injection of botulinum toxin A is effective in reducing the frequency of oscillations in children with horizontal nystagmus both 1 and 6 months after the procedure, and can be used as a first-line, less invasive treatment aiming to decrease the frequency of oscillation. [J Pediatr Ophthalmol Strabismus. 20XX;X(X):XXX-XXX.].

Golden Indications and an Overview on the Use of Botulinum Toxin in Strabismus

Botulinum toxin A (BTXA) is considered a pharmacological agent that may provide an alternative treatment to surgery in strabismus. It can be used as both a diagnostic and therapeutic agent in various concomitant, paralytic, and restrictive disorders. The major advantage of BTXA treatment is that it is non-invasive and does not impact the patient's chance for future surgery in case of an unfavorable response. In some selected disorders, BTXA has become the primary choice of treatment, whereas surgery is found to be more effective in others. Accumulated knowledge and experience have demonstrated that BTXA is more than merely an alternative treatment and has additional specific indications such as in unstable deviations and as an adjunct to surgery. Patients with recurrent deviations despite multiple surgeries are also good candidates for BTXA treatment. Although the major expectation is to obtain a permanent result, BTXA can also be used as a maintenance treatment. This paper mainly focuses on the current indications for the use of BTXA in strabismology, with special emphasis on ideal first-choice applications referred to as "golden indications," within the scope of the author's own experience with the use of BTXA over 30 years.