I've definitely seen fairy tales where blind (and blinded) characters are, in fact described as that (in the fairy tale Rapunzel, for example, and the Aesop fable of "The blind man and the lame man"). I, personally, wouldn't call "blind" a diagnosis, any more than "tall," or "round." Optic neuropathy, on the other hand...

As for a modern-day setting for a fairy tale, I was thinking more philosophically: Not just in terms of magic realism (where the "world of the fae" is just on the other side of a very thin veil, and keeps crossing over into every day lives (J.R.R. Tolkien defined a story as a "Fairy Tale" as a story that deals with an Other-World of magic, not necessarily a story with actual fairies flitting about), but a story that also treats its characters and setting more as metaphors for the human condition than discrete examples of individuality.

(After all, when Perrault penned his version of Cinderella, the social convention of royal balls and carriages and footmen was all contemporary.)