Help!! My dog!!!?

I was brushing my dog and noticed behind his front left leg there was a totally bald spot. No hairs. It was kind of flaky looking. About the size of a large golf ball. I also think he might have eye problems because he doesn't seeing things that are right infront of him. You have to show it to him at his side then point it out to him when you put it on the ground. He can find things well by sound. If I kick a soccer ball he will run and usually find it no problem(usually). When we first got him he used to run head on into the solid wood coffee table. I am worried about him. He is a large border collie we rescued from the local aspca. His pupils are always very large. They are typically just a bit short of the overall size of the colored portion of his eye. I just want to know if I can help, or what I should do, or what he might have.