The beauty of clickies is that their mental condition is whatever you want it to be, so I doubt they will do anything with that since its not needed.
However they can of course have children with glasses, wheelchairs outside the hospital theme, fat children, and blind clickies can be represented with sunglasses, a walking stick and helper dog.
Though I gues it would be difficult for actual blind people to play with playmobil, it can help to create understanding for the blind.
Personly being someone who had glasses for as long as I can remember, I never took note of clicky children not having glasses though. It never bothered me but then again, I never had much of an urge to identify myself as a clicky.