Convergence spasm treated with botulinum toxin

To analyze the effectiveness of botulinum toxin injection for convergence spasm.

Review of the Toxin Clinic database to identify patients who had undergone botulinum toxin injection to the medial rectus muscle for convergence spasm.

There were 11 females and 6 males. Average age at treatment was 34 years (range 12-57 years). All patients had a variable esotropia, ranging from 10 to 90+ prism diopters but most could demonstrate some binocular function. All patients had convergence spasm, pupil miosis, and diplopia. Previous treatment included surgery, atropine, plus lenses, and occlusion. Fourteen patients (82%) were temporarily overcorrected after their first injection. Three patients (18%) were symptom free after just one injection and were subsequently discharged, all having been temporarily overcorrected. Seven patients (41%) continue with botulinum toxin on a regular basis, with or without occlusive contact lens, to remain symptom free, two being discharged after the third and fifth injections symptom free. Seven patients found no benefit from this treatment and so were discharged from the clinic or did not attend for follow-up appointments.

Our rather extensive experience with these patients has led us to conclude that in some patients convergence spasm may be a type of dystonia, and may like other dystonias be suitable for botulinum toxin treatment.