What is the phenomenon of seeing light without light actually entering the eye called?

A phosphene is a phenomenon characterized 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 that are induced by movement or sound may be associated with optic neuritis.

Phosphenes can be directly induced by mechanical, electrical, or magnetic stimulation of the retina or visual cortex (a part of the brain which processes visual information) as well as by random firing of cells in the visual system. Phosphenes have also been reported by meditators (commonly called nimitta), people who go for long periods without visual stimulation (also known as the prisoner's cinema), or those who are using psychedelic drugs.