Botulinum Toxin Injection With Reduced Volume in the Absence of Electromyographic Assistance for Acute Acquired Comitant Esotropia of 25 Prism Diopters or Less.

[PURPOSE] To evaluate the effectiveness and safety of botulinum toxin type A (BTXA) injection with reduced volume without electromyographic guidance for the treatment of acute acquired comitant esotropia (AACE) of 25 prism diopters (PD) or less.

[METHODS] The authors reviewed the medical records of 60 patients with AACE of 25 PD or less, including 40 patients treated with BTXA injections (BTXA group) and 20 patients treated with Fresnel prism (Fresnel prism group). Patients in the BTXA group were injected with 5 to 6.25 U of BTXA in 0.04 mL of saline into bilateral medial rectus muscles in the absence of electromyography. Patients in the Fresnel prism group wore Fresnel prisms at a minimum amount that could eliminate diplopia. Success was defined with deviations of 10 PD or less at both distance and near fixations and with resolution of diplopia.

[RESULTS] In the BTXA group, the success rate of the first injection was 100% after 1 week, but decreased to 57.5% (23/40) after 6 months; the cumulative success rate of two injections was 77.5% (31/40) after 6 months; and one eye (0.93%, 1/108) had complicated mild ptosis. In the Fresnel prism group, the success rate was 5% (1/20) after 6 months of treatment. The difference in cumulative success rate between the two groups was significant (chi-square = 28.158, < .01).

[CONCLUSIONS] BTXA injection with reduced volume in the absence of electromyography is a simple, effective, and safe modality for patients with AACE who have a small to moderate deviation. .