Zonisamide-induced angle closure and myopic shift.

Purpose: To present a previously unreported case of angle closure secondary to the sulfonamide derivative zonisamide, to introduce eye care providers to zonisamide, and to review sulfonamide-induced angle closure. Zonisamide is a relatively new sulfonamide derivative indicated for epilepsy and used off-label for migraines. Although angle closure secondary to systemic medications such as topiramate and other sulfonamide derivatives is well documented, this is the first case of zonisamide-induced angle closure and myopic shift to be reported.

Case Report: A 39-year-old Hispanic woman presented with sudden vision loss OU with a concurrent bilateral frontal headache. No changes in health were reported other than initiating zonisamide for refractory migraines 2 weeks prior. Ocular history was significant only for low myopia. Entering visual acuities were 20/400 OD, OS. Manifest refraction revealed a 3-diopter myopic shift OU with best-corrected visual acuities of 20/20 OD, OS. On slit lamp examination, the anterior chamber angles were narrow OU and gonioscopy confirmed partially occluded angles OU. The intraocular pressures were elevated OU. B-scan ultrasonography exhibited peripheral choroidal effusion OU. With discontinuation of zonisamide, the patient experienced full recovery.

Conclusions: With increasing use of zonisamide, practitioners should be aware of its sulfonamide derivative properties and the risk of secondary angle closure.