Electroretinography (ERG) Monitoring for Vigabatrin Visual Toxicity (The Pros and The Cons) - ERG versus No ERG with; Clinical Follow-Up (ERG Beneficial & ERG Not Beneficial)

Pro: Eleven years ago, FDA approval of vigabatrin treatment for complex and refractory childhood epilepsy in the United States added substantially to previous experience in Europe, Canada and elsewhere. This experience has revealed both its utility in a wider variety of complex, refractory seizure disorders and its retina to the optic nerves and central nervous system (CNS) structures. Basic research has pointed towards several underlying pathophysiologic mechanisms of visual loss, which may interact variably with patients' underlying neurodevelopmental diseases. Con: Vigabatrin is a known cause of ocular toxicity and visual field loss. Early reports estimated ocular toxicity at 52% in adults and 34% in children. However, most early data was from small, retrospective studies and, crucially, many patients did not have baseline visual testing and had been on long-term treatment with vigabatrin. Due to the reports of ocular toxicity, the Food and Drug Administration (FDA) started a mandatory drug registry for vigabatrin with robust visual function testing. From 2009 to 2016, 1,509 patients had ophthalmic testing and only 2% had a potential vigabatrin-associated effect on vision. Furthermore, many of the cases of potential toxicity returned to normal on repeat testing. Interestingly, 37% of the cohort did have pre-existing pathology affecting the visual system, which might have been interpreted as toxicity had baseline testing not been done.