The effect of antiepileptic drugs on visual performance.
Visual disturbances are a common side-effect of many antiepileptic drugs. Non-specific retino- and neurotoxic visual abnormalities, that are often reported with over-dosage and prolonged AED use, include diplopia, blurred vision and nystagmus. Some anticonvulsants are associated with specific visual problems that may be related to the mechanistic properties of the drug, and occur even when the drugs are administered within the recommended daily dose. Vigabatrin, a GABA-transaminase inhibitor, has been associated with bilateral concentric visual field loss, electrophysiological changes, central visual function deficits including reduced contrast sensitivity and abnormal colour perception, and morphological alterations of the fundus and retina. Topiramate, a drug that enhances GABAergic transmission, has been associated with cases of acute closed angle glaucoma, while tiagabine, a GABA uptake inhibitor, has been investigated for a potential GABAergic effect on the visual field. Only mild neurotoxic effects have been identified for patients treated with gabapentin, a drug designed as a cyclic analogue of GABA but exhibiting an unknown mechanism while carbamazepine, an inhibitor of voltage-dependent sodium channels, has been linked with abnormal colour perception and reduced contrast sensitivity. The following review outlines the visual disturbances associated with some of the most commonly prescribed anticonvulsants. For each drug, the ocular site of potential damage and the likely mechanism responsible for the adverse visual effects is described.
Hilton
Emma J Roff
EJ
Neurosciences Research Institute, School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham B4 7E7, UK.
Hosking
Sarah L
SL
Betts
Tim
T
D000927:Anticonvulsants / Q000009:adverse effects* / Q000145:classification; D003118:Color Perception / Q000187:drug effects; D015350:Contrast Sensitivity / Q000187:drug effects; D004172:Diplopia / Q000139:chemically induced*; D004305:Dose-Response Relationship, Drug; D004585:Electrooculography; D004827:Epilepsy / Q000188:drug therapy*; D005074:Evoked Potentials, Visual / Q000187:drug effects; D006801:Humans; D014792:Visual Acuity / Q000187:drug effects*; D014794:Visual Fields / Q000187:drug effects*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D000927:Anticonvulsants; D005680:gamma-Aminobutyric Acid