Effects of the periocular botulinum toxin on the ocular surface and anterior chamber: a prospective study in patients with hemifacial spasm and blepharospasm.

PURPOSE: To analyze using Pentacam®, the corneal and anterior chamber changes following periocular botulinum toxin injection in patients with facial dystonia. METHODS: Prospective study that included patients with facial dystonia that were going to receive a periocular botulinum toxin injection for the first time or six months or more after the previous injection. A Pentacam® examination was carried out in all patients before and 4 weeks after the injection. RESULTS: Thirty-one eyes were included. Twenty-two had a diagnosis of blepharospasm and nine of hemifacial spasm. Analysis of corneal and anterior chamber parameters revealed a significant decrease in iridocorneal angle after botulinum toxin injection (from 35 ± 10º to 33.8 ± 9.7º, p = 0.022). No other corneal or anterior chamber parameters changed significantly after the injection. CONCLUSIONS: Periocular botulinum toxin injection causes narrowing of the iridocorneal angle.