Intermittent photic stimulation can induce epileptic seizures in some patients. These seizures may take various forms which are characterized by overt phenomena or atypical EEG signals. Many adventitious stimuli in the environment have been found to be capable of producing these attacks. The neuropbysiological mechanisms underlying this condition are only partially understood, and are the subject of considerable research effort at the present time. Various therapies have been proposed including some involving spectacle devices.