A phosphene is an entoptic phenomenon characterize by the experience of seeing light without light actually entering the eye. The word phosphene comes from the Greek words phos (light) and phainein (to show). Phosphenes can be directly induced by mechanical, electrical, or magnetic stimulation of the retina or visual cortex as well as random firing of cells in the visual system. Phosphenes have also been reported by people who go long periods without visual stimulation (also known as the prisoner's cinema) or under the influence of drugs, especially a hallucinogen.