Photosensitive epilepsy. Electrophysiological aspects

Intermittent light stimulation (ILS) is more effective to trigger electroencephalographic paroxysms when the patient remains with his eyes closed. In order to evaluate the relative value of the different factors involved, 9 patients of matched age and sex were studied. EEG with ILS, electroretinogram and visual evoked potentials with a flash stimulus were performed under different conditions: open eyes with white, red and blue light, closed eyes and diffusing screen. Analysed in toto, results obtained in the different studies suggest that (a) the factor with greater capability to produce alterations in photosensitive epilepsy is the diffusion of light encompassing a bigger area of the stimulated retina and (b) not only the brain structures but also the retina itself would be involved in the mechanisms underlying the phenomenon of photosensitivity in these patients.