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Thomas B Connor; Clinical and electroretinography features observed in patients taking ezogabine.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):765.
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To present clinical and electrophysiologic features of patients taking the anti-seizure medication ezogabine. FDA warnings from 4/26/13 anounced that ezogabine can cause blue skin disoloration and eye abnormalities characterized by pigment changes in the retina, though detailed information has been limited.
Retrospective chart review of patients taking ezogabine referred by the neurology service for ophthalmic examination. Charts were reviewed for features of ophthalmic examination and additional testing of ganzfeld electroretinography (ERG), perimetry, and imaging using auto-fluorescence, wide-field fundus imaging, and retinal optical coherence tomography (OCT).
Six patients were identified:4 men and 2 women aged 18-63 yrs (mean 46.8). All had long histories of seizure disorders that had been diificult to control, often requiring multiple trials of medications and surgery. One patient had used ezogabine for 11 months, stopping because of muscle irrritation. The other 5 had used ezogabine for 1.5 - 2yrs ( mean 1.8 yrs). All patients denied any visual symptoms. No abnormal coloration of skin, nail beds, lips, or sclera was noted. Visual acuity, Ishihara color vision testing, and perimetry were unaffected. Ocular examination was unremarkable save for two patients with mild pigment mottling of the inferior post-equatorial RPE. Autofluorescence and macular OCT were unremarkable. Ganzfeld ERG results were unremarkable in 3 patients. 2 patients demonstarted a reduction in photopic/cone response (with essentially unaffected scotopic/rod response) and 1 patient had extinguished rod and cone responses, demonstrated on two separate testings 2 months apart.
Ophthalmic findings including ganzfeld ERG features are described in 6 patients who had used ezogabine for 1-2 years. ERG findings ranged from normal in 3 patients to reduced response in 2 patients and extinguished in 1 patient. All patients noticed no visual symptoms and had unremarkable exams save for two patients with mild RPE pigment mottling. Detailed examination with extended follow-up of a larger population of patients on ezogabine may help our understanding of the significance of these findings.
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