Acute effects of sildenafil on the electroretinogram and multifocal electroretinogram

PURPOSE: To evaluate the acute effects of sildenafil (Viagra; Pfizer, Inc, New York, New York) on the electroretinogram and multifocal electroretinogram. METHODS: Eighteen healthy individuals (ages 21-49 years) were studied; 14 were given 200 mg sildenafil orally and four were given only water. All subjects were tested before sildenafil and 1 hour after sildenafil (or water) with a desaturated Panel D-15 color test, a full-field standard electroretinogram, and a multifocal electroretinogram using the VERIS system; five subjects were also tested 5 hours after sildenafil. RESULTS: Responses from the subjects who received sildenafil were compared with those from the control subjects. At 1 hour after sildenafil, photopic single-flash waveforms were attenuated by 9% and scotopic maximal response amplitudes were increased slightly. Photopic and 30-Hz flicker electroretinogram responses were delayed; multifocal electroretinogram waveforms were delayed (5%-9%) and attenuated (14%-22%) across the posterior pole. These changes did not resolve by 5 hours. Nine of the subjects who had received sildenafil (64%) reported visual or systemic symptoms, including one who reported bluish vision. Ten of those subjects (71%) showed a slight increase in color test errors 1 hour after sildenafil. CONCLUSIONS: For at least 5 hours after taking 200 mg of sildenafil, cone function was slightly depressed in the macula and periphery, as measured by full-field electroretinogram and multifocal electroretinogram recordings. However, the affected electroretinogram and multifocal electroretinogram parameters still remained within normal limits.