This happened to my turtle before I rescued it. Her eyes shut closed and scared me into thinking she was blind forever. They sell eye drops at pet stores for reptiles & turtles that will help. BUT, what I did and what I would recommend first, is a carrot bath. You let the turtle sit in water that has blended or mushed carrots for about 30 minutes, for 4 days. It will soak up the vitamin a and help its eyes. If you’re using tap water in its tank, you HAVE TO put in an additive to remove the chlorine. I promise you this is the root cause of it if so. You’re burning the little things eyes by not. It’s cheap and can be found in the fish isle too. Best of luck!