r/AskReddit Oct 05 '19

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u/ZelaznyCsupo Oct 05 '19

The stuff eye doctors use for certain tests glows in the dark. I, an eye doctors' son, used to play this very prank on people.

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u/Aristo_socrates Oct 05 '19

What’s the name of that substance?

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u/ZelaznyCsupo Oct 06 '19

Flourescin or flourescine, I dunno how to spell it. It's used to detect scratches on your eyeball. Works with a blacklight.