Photosensitivity: the magnitude of the problem.

Very few studies of photosensitivity or visual sensitive epilepsy could be called epidemiologic in the strict sense, that is, giving well-based incidence and prevalence rates of a well-defined clinical and electroencephalographic syndrome or group of syndromes. The available data suggest that photosensitivity is rare in the population as a whole, with an annual incidence rate around one case per 100,000 population. The incidence goes up to almost six per 100,000 in the late adolescent period, the age group at the highest risk. Well-established concepts, such as statements that one in 4,000 of the general population or that 10% of all epilepsy patients would be photosensitive, should be reevaluated. The more likely figures are a lifetime prevalence of one in 10,000 in the general population, perhaps as low as 2%, of the epilepsy population. Further epidemiologic studies, sensu strictu, are warranted to settle the basic question of the real incidence and prevalence of photoparoxysmal responses (PPRs) and epilepsy with seizures provoked by visual stimuli in the community.