The corneas of 50 normal subjects were examined before and after electroretinography performed with gold foil electrodes. Examination included slit-lamp biomicroscopy and staining with sodium fluorescein. All corneas were normal on examination prior to electroretinography. Three types of transient corneal changes were observed--punctate epithelial keratitis, corneal erosions, and stromal thinning. Each cornea was assigned a numerical damage score based on a simple scoring system. Thirty one subjects (62%) had some degree of corneal change, and in three cases (6%) follow-up was required. Multiple regression analysis was performed to discover any risk factors. Both age of the subject and the use of local anaesthetic were strongly associated with corneal changes.