Electroretinography (ERG) Monitoring for Vigabatrin Visual Toxicity (The Cons)

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.