Going, Going Gone...Toby's eyesight, that is...

Our biggy boy seemed totally blind tonight. We had a play date with Trouble and Sugaree, this afternoon. After dinner, Toby was walking around upstairs very slowly (as in slow-motion), one paw being put down cautiously after another. He didn't seem to know where he was at any given time. Could all the jostling of hard play have finally been the nail in the coffin of his eyesight? He will be 5 years old in October, and we have been hoping that he would maintain a small amount of sight, but that hope may have now flown...