Topiramate associated non-glaucomatous visual field defects

• A rare case of non-glaucomatous visual field deficit secondary to topiramate use is presented.
• The underlying mechanism may be similar to vigabatrin–like GABA accumulation in the retina.
• Concurrent maculopathy and pre-existing myopia and keratoconus may be contributory as well.
• Baseline and follow up visual field assessments may help in early detection and better delineation of these mechanisms.

We report a 34-years-old woman who presented with bilateral incongruous inferior visual field defects after the commencement of topiramate for management of migraine. Investigations did not reveal any underlying angle closure glaucoma, reported in current literature to be associated commonly with topiramate associated visual field defects. The changes in the peripheral visual fields gradually improved over several months after the medication was withdrawn. There were only minor changes persistent on the left side on a background of pre-existing myopia and keratoconus. Visual field deficits secondary to topiramate are more commonly attributed to angle closure glaucoma due to ciliochoroidal effusion syndrome. In such instance, the visual field defects are associated with considerable pain due to raised intra-ocular pressure. There have also been reports of visual scotomas due to retinal damage and maculopathy in patients taking topiramate. It is worthwhile to obtain a baseline perimetry in patients being considered for topiramate therapy in order to gauge any changes in their peripheral field of vision during the treatment. Changes in visual fields during the course of medication use and after cessation can be easily compared especially if there are other possible confounders such as refractive errors or a history of migraine.