Concerned about new cat?

While on vacation in Galveston I came across a stray who decided it would camp on our dock for three days straight. She is very sweet but I think something is wrong with her. Possible blind, and deaf. She also sneezing a lot. The reason I think she may be blind and deaf is because she reacts very little to me waving my hand in front of her face. When I do this it's like she notices it then loses sight of it, even when I only wave it slowly. Also I clapped really loud directly in front of her face and she did not react what so ever. She just sat there. I'm wondering if she is just maybe mentally retarded or if she is really bind/deaf. Oh and she is eating and drink fine, but not using the litter box.