We probably wouldn't know unless (a) one of their species is canonically blind (IE a Zubat), doesn't like opening their eyes (IE an Abra), or an evolution thereof, or (b) we interview them with a very positive rapport and they spill the beans that they were/used to be blind and thus knew Braille.

Rather puzzling, to say the least.

In any case, can someone ship back the Temperate War to that poor Swinub so we can get that Oran Berry? That'll probably be useful down the road.