Purpose: To evaluate the effects on vision in patients receiving lamotrigine (LTG) monotherapy.
Methods: Twenty-four consecutive patients taking LTG for partial seizures were referred for a routine ophthalmologic examination including visual acuity testing, tonometry, slit lamp, and fundus examination. Automated kinetic perimetry, electrooculogram (EOG), and electroretinogram were performed after informed consent was obtained.
Results: In 18 patients finally included, the clinical ophthalmologic examination showed no abnormality. Four patients complained of blurring; among them, one patient had a visual field constriction in both eyes, which, however, was of unclear clinical significance (poor compliance) and a reduced light/dark ratio of the electrooculogram. One other patient with blurred vision had a reduced EOG, but the visual field was normal. Two patients had a reduced EOG but no visual symptoms. Considering the whole group of patients receiving LTG therapy, the light/dark ratio of the EOG was reduced in a dose-dependent fashion (p < 0.0001). The electroretinogram was normal in all patients.
Conclusions: No irreversible visual field impairment in patients treated with LTG was encountered, although a dose-dependent retinal toxicity may have been present. The exact cellular mechanism of the electrophysiologic changes in patients taking LTG remain to be explained.