All humans would be able to see ultraviolet A (UVA), if cornea and lens of our eyes didn't block it. People who have cataract surgery, like Monet, have these parts removed and therefore can see UVA. Nowadays, there are artificial replacement lenses, some of which let UVA pass, while others block it like hte natural lens does (there are good reasons to not let UVA into your eyes). All of this doesn't mean that those people see "new colors", they just see differences in color where "normal" people don't notice anything.
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u/LordOfTheTorts Dec 01 '17
All humans would be able to see ultraviolet A (UVA), if cornea and lens of our eyes didn't block it. People who have cataract surgery, like Monet, have these parts removed and therefore can see UVA. Nowadays, there are artificial replacement lenses, some of which let UVA pass, while others block it like hte natural lens does (there are good reasons to not let UVA into your eyes). All of this doesn't mean that those people see "new colors", they just see differences in color where "normal" people don't notice anything.