My 18 yr.old leopard gecko stopped eating?

He also became blind in both eyes within the last few months. He stopped eating for the past few weeks and since being old, I have been hand-feeding him for the last couple of years (too slow to catch crickets) I have been feeding meal worms, but lately he won't take them. I got some wax worms and he didn't want those either -- even after I put one in his mouth, he just spits it out. I have been able to give him some water with an eye dropper and he has finally peed. His tail is becoming thinner than I've ever seen it. Could it be he just wants to die? Could it be he is constipated from meal worms? I don't want to just wait for him to dry up. I do have some vitamin spray to spray ON him. Will this help him? Any other suggestions?