Vigabatrin
- Anti-epileptic agent used mainly for refractory childhood seizure disorder called infantile spasms
- Most such children are cognitively impaired
- Ophthalmic side effect: visual field constriction
- Attributed to effect of excess neurotransmitter GABA on retinal photoreceptors and ganglion cells
- Children do not report symptoms because they are neurologically impaired and vision deficits are subtle
- Ophthalmoscopy normal unless damage advanced
- Visual field constriction and optic disc pallor indicate advanced damage
- Electroretinography may disclose abnormalities
- Try not to exceed daily dose of 100mg/kg
- Withdraw this medication if ineffective
- FDA requires that children undergo baseline and serial ophthalmic examinations, but
- These children not able to cooperate for visual function testing or electroretinography, so...
- Serial ophthalmoscopy may be only way to monitor for retinal toxicity, yet...
- Ophthalmoscopy insensitive to toxicity
- Peripheral visual field loss may occur but unlikely to be disabling, and...
- Visual field loss may be reasonable trade-off for seizure control