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.