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[Visual field changes secondary to vigabatrin treatment].

INTRODUCTION
Vigabatrin is an effective antiepileptic drug for treatment of partial crises with or without generalization. It acts by increasing GABA levels by irreversible inhibition of the enzyme GABA-transaminase. In recent years there have been several reports published on the appearance of alterations of the visual fields of patients treated with this drug.


OBJECTIVE
To study the prevalence and characteristics of the visual field changes associated with vigabatrin treatment in an adult epilepsy clinic.


PATIENTS AND METHODS
Ophthalmological examination, consisting of questions about eye symptoms, study of the fundus oculi, Humphrey-type campimetry, protocol 30-2, visual evoked potentials and electroretinogram were done on a group of 10 patients on long-term vigabatrin treatment.


RESULTS
Six of the ten patients (60%) had campimetric alterations, which were serious in two cases (20%). Only the two patients with severe field defects complained of sight changes when questioned and their complaints were mainly of repeatedly bumping into things. In two patients (20%) there was pallor of the optic nerve. In both cases, the patients with severe field defects showed alterations on the electroretinogram. Visual evoked potentials were normal in all cases.


CONCLUSIONS
There is a very high prevalence of visual field defects in patients on long-term treatment with vigabatrin. Clinical ophthalmological signs are not usually seen until advanced stages. Pallor of the optic nerve was seen in a group of patients. It is very important that serial campimetric studies are done for early detection of such alterations.