Types of photosensitivity, prevalence and other characteristics of the photoparoxysmal response (PPR), associated seizures, effect of video games, and drug therapy are reviewed by the director of electroencephalography at the University of Illinois, Chicago. Photosensitivity has been graded according to the spread of epileptiform activity: occipital, parietal-occipital, also involving frontal areas, and generalized spike and wave complexes. The majority (65%) of PPR patients have had spontaneous epileptiform abnormalities, generalized spike and wave or partial, temporal lobe, or central rolandic multifocal sharp waves. The prevalence of PPR has diminished over time; in the 1960s it was 3% of all patients having an EEG in this laboratory, whereas now it is a rare occurrence. Studies after 2000 find a prevalence of 0.8%, 1.7% in children, and 1.8% in patients with clinical seizures. PPR is more common in Caucasians and females. Mean age is 12 years. PPR occurs at the moment of eye opening or closing, and predominantly at a flicker frequency of 15-16 Hz and wavelength of 700nm. Inheritance is autosomal dominant. Luminance studies with sunglasses show variable results in the suppression of PPR. A deep red color is required for induction of PPR. In the prevention of the video game Pokemon effect, blue lenses inhibit the PPR by the short wave length and diminished illumination. Seizures evoked by video games are a manifestation of photosensitive epilepsy. During the PPR 75% patients experience impaired consciousness, opening of eyes or jerking, and pain in the eyes. Persistence of PPR after stimulation is ended is not associated with a higher risk of seizures. Other abnormalities in the EEG, not the PPR are significant in the cause of post- PPR seizures. Prognosis is generally good, especially after age 20 years. Valproic acid and levetiracetam are effective in eliminating PPR. 
COMMENT. Spikes confined to the occipital region and time-linked with photic stimulation may be a normal finding. Seizures evoked by photic stimulation are usually primary generalized: generalized tonic-clonic, absence, or myoclonic. Photosensitive seizures are classified as pure, occurring only during exposure to photic stimulation, or complicated by spontaneous seizures in addition. Some patients derive a pleasurable response to a self-induced seizure by waving their hands in front of their eyes.