Why would it care? Cats seem able to sleep just fine with lights on. Or off. Or flipping on & off as people move around. Or with the TV, radio, or stereo blaring. Or all of them blaring at once, on different channels.
Cats can sleep through all that. Nothing wakes them – except the quiet whirr of the can opener way back in the kitchen – they can hear that from 2 floors away!
Our apartment has a very long hallway, with all the rooms off to the right of it from front to back. There is very little light down that hallway, even during the day, and the cat litter is in a windowless storeroom near the middle of the hall. Our two cats have no trouble finding their way, day or night. They don’t need night lights.
No cite, but it’s common for cats (and dogs) to slowly lose their sight without anyone noticing … until someone rearranged the furniture!
I had ferrets in college. Never knew one of them was blind until Mr. Horseshoe poked her directly in the eyeball (accidentally) and she didn’t blink. Didn’t even care. But ferrets can’t see all that great to begin with, and navigate through their whiskers and sense of smell - just like cats, OP! - so I had friends who insisted to me that no, she couldn’t possibly be blind. I’d had her for years before we realized she couldn’t see, so I understand their insistence.
Also, how could anyone think that “cats see well in the dark” is a myth? Maybe OP’s wife needs to spend a little time on Wikipedia, or literally any reputable cat care website (or book). Neat diagrams of feline eyeballs might help convince her!