Palinopsia

How it works

Palinopsia means “seeing again”. It is the name for any image that continues or comes back after the thing you saw is no longer there¹. A normal afterimage is not palinopsia. Afterimages come from tired cells in the retina and show up in reversed colours. Palinopsia comes from the brain and keeps the original colours and detail³.

Doctors split it into two types¹.

Illusory palinopsia is short and depends on the conditions. Moving objects leave a trail of copies behind them, like a strobe photograph. A bright object leaves a copy that lingers for seconds. It happens more in dim light and with high-contrast objects¹. Many people notice a mild form when they are tired, during a migraine, or when they have visual snow. It is also a well-known effect of some drugs¹.

Hallucinatory palinopsia is different. A complete, detailed image of something seen earlier reappears after a delay, often minutes later, and may last a long time. It does not depend on light or contrast¹. This form is linked to damage or irritation in the visual parts of the brain, for example from a stroke, a tumour, or seizures, and it needs a medical work-up¹.

The mechanism for the illusory type is thought to be a visual system that is slightly too excitable. Signals that should switch off keep going, so the previous image is not cleared fast enough¹.

Is it a problem?

Brief trails behind moving lights, especially when you are tired or in the dark, are common and are not a sign of disease¹. If they are part of visual snow, they tend to stay stable for years.

See a doctor if you see full, detailed copies of objects or people that return minutes after you looked away, if the copies stay in one part of your vision, or if the symptom is new and comes with headache, weakness, or confusion. Those patterns need an examination and usually a brain scan¹.