My parents old cat lost her sight with old age, and she coped with it fine, so long as you didn't move the furniture.
One Christmas, one chair that she favoured sleeping on, had been moved exactly it's width sideways, and Cindy wandered into the room, brushed up against the leg to check that she was by the chair, and then jumped up, only to fall flat on her face! It was quite amusing, even if the poor cat probably didn't understand what had happened.