BTA injection to treat convergence insufficiency
Reviewed by Fiona Rowe

The outcomes of patients with convergence insufficiency (CI) treatment with botulinum toxin A (BTA) in one or both lateral rectus muscles are reported. This was a retrospective study of 23 patients; eight males, 15 female, mean age 59 years (range 23-81). Twenty-one had tried convergence exercises, and 21 had tried prisms. Two had surgery for CI and two had surgery for other strabismus. Five had a history of head trauma. Median best corrected visual acuity was 1.0 logMAR. Unilateral BTA injection was done in all but one patient. Median deviation angle at near was 18PD (13-21) reducing to 10PD (907-17) after BTA and 14PD (12-18) at last follow-up. At distance medial deviation angle was 4PD (2-7) reducing to 2PD (0.5-6) after BTA and 4.5PD (2-6) at last follow-up. Near point of convergence did not change over time. 57% reported improvement in reading symptoms, 39% reported no change and one had worsening of symptoms. 65% opted for repeat BTA. The authors conclude BTA is a useful treatment for some cases of CI but repeat injection may be necessary.

Botulinum toxin A injection for convergence insufficiency.
Hofsli M, Torp-Pedersen TE, Lonkvist CS, Saunte JP.
JOURNAL OF PEDIATRIC OPHTHALMOLOGY AND STRABISMUS
2023;60:108-13.