Why do I see stars when I push my eyes?

'Oh, oh, everybody's starry eyed...' when you press down too hard on closed eyelids it can appear as though lights are flashing. 

22nd July 2009
What causes the light under my eyelids when I put pressure on my closed eyes? (Getty)

Asked by: Dale Wilkinson, Guildford

Pressure on the eyeball compresses the retinal artery. You don't have to press terribly hard to cut off the blood supply to the retina entirely.

Deprived of oxygen, the photoreceptors can start firing randomly, causing swirling colours or flashing lights. It's a similar phenomenon to the stars you see when you stand up too suddenly.


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