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 are often associated with optic neuritis.

Phosphenes can be directly induced by mechanical, electrical, or magnetic stimulation of the retina or visual cortex 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.

De Ridder et al. describe a case of intermittent paroxysmal unilateral phosphenes (i.e., light flashes) associated with worsening visual field defects. Magnetic resonance imaging (MRI) demonstrated a sandwiched optic nerve/chiasm between an inferior compression of the internal carotid artery (ICA) and a superior compression of the anterior communicating artery (ACoA). He was successfully treated by a microvascular optic nerve decompression and anterior clinoidectomy plus optic canal unroofing.

This case report adds to the few previous case reports in combining 2 previously described techniques, i.e. microvascular decompression and anterior clinoidectomy plus optic canal unroofing ¹⁾.