eye problem

by Jason
(Texas)

Hello, My sulcata tortoise is about 80 lbs, and I've just started noticing his left eye will shut, and stick out a little bit, and it is white. He does it when he is eating, and it seems to bother him a little bit. He will rub it on his leg. it seems to get stuck that way for a short time, and then will go back to normal. After it goes back to normal, I notice his eye watering up a little bit. What is cause? How can I fix the problem?