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The Daily Cardinal Est. 1892
Sunday, February 25, 2024

Ask Ms. Scientists: Physical retina stimulation causes geometric hallucinations

Dear Ms. Scientist,

Why do I see bright geometric shapes when I rub my eyes?    

                         —Haley W.

Waking up from your power nap, you rub your eyes and see bright geometric shapes as if there’s a kaleidoscope on your eyelid. The colorful shapes are called phosphenes and this effect is called an entopic phenomenon, meaning that the hallucinations are coming from inside your eye.

Putting pressure on your eyes stimulates your retina, the part of the eye that transforms what you see into brain waves. The retina is thus very metabolically active and sensitive in order to account for all the visual changes you see and send them to your brain quickly and accurately.

As a result of physical instead of light stimulation, the retina’s photoreceptors start to fire abnormally, making your brain think that it is seeing images, a.k.a. phosphenes.

Ask Ms. Scientist is written by Corinne Thornton. If you have a burning science question you want her to answer, email it to

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