Well if you r sure he is blind I would put him in a very small cage with only a enough water to cover him to the tallest part of his shell with a regular light and when you feed him put him in a bole of some sort with no water and put the food in a circle around him and I would get him checked out by a vet to make sure there is nothing else wrong with him.
P.S. I hope it is only temporary and I am sorry for you and your turtle
P.S. I hope it is only temporary and I am sorry for you and your turtle