Seeing flashes from sounds

How it works

A phosphene is light that you see without light entering the eye⁶. An auditory-evoked phosphene is a flash, a patch of colour or a simple shape triggered by a sudden sound¹⁴.

Most published cases are people who have lost some vision, usually from damage to the optic nerve²⁴. In reports from 1981 and 1982, flashes appeared in the damaged part of vision⁴⁵. In 1982, they disturbed sleep⁵.

Healthy people can see it too, in the dark. In a 2019 study, students sat with their eyes closed in a dark room while short beeps played at random times¹. Louder beeps caused more flashes, and flashes tended to appear on the side of the sound¹.

The cause is not proven. In everyone, sounds change activity in the visual brain, but normally you see nothing¹. One idea is that less visual input makes this weak link strong enough to see¹³.

Unlike lifelong synesthesia, which starts in childhood², these flashes usually come after vision loss or time in the dark¹².

How common it is

No one knows how often people notice this in daily life. After the 2019 study sessions, 44 of 77 students (57%) said the sounds had made them see something¹. During the sessions, 24%, 68% and 72% reported a flash in three experiments¹. The students knew they might see flashes, which could bias the answers¹. A 2009 review listed 20 published cases in people with vision loss².

Try it

1. Sit in a fully dark room with your eyes closed for at least 5 minutes.
2. Then ask a friend to play a short beep at random moments, about 40 seconds apart.
3. Watch for a flash or a patch of colour just after each sound.

Keep the sounds at a normal loudness and away from ears. Many people in the study saw nothing, even in a half-hour session¹.

Is it a problem?

In a healthy person sitting in the dark, it appears to be common¹. But most published cases come from people with damage to the optic nerve². See a doctor promptly if flashes with sounds:

• are new and happen in ordinary daily life,
• appear in one eye only,
• come with blurred vision, a dark patch or other loss of vision.

History and culture

In 1979, Lessell and Cohen described three adults who saw flashes from sounds in a dark or dim room. Two had optic nerve disease. One had had a transplant of the clear front of the eye³. The authors called the flashes a kind of hypnagogic hallucination, the images seen at the edge of sleep³. Some healthy people also report such flashes, typically just before sleep¹.