I just have to say I'm going through something similar my baby girl is 17 too & she has developed cataracs. She can see some motion, but she often has walk next to the wall to keep her bearings. She sees better in the day light than at night, but all in all she does fine not being able to see. She can find her food & water bowls. She has not gone outside of her box even once. In the mornings she will even get in the bed with me. I had to turn a laundry basket upside down next to the bed for her to be able to get in the bed but now I wake up with her sleeping right next to me every day. I agree that things should not be changed because he is aware of the current layout, and I think if his vision is the only problem he has at 17 your blessed because my baby has CRF & that is a battle no one should have to fight.