Hi--Does your chin seem to have any discoloration either in one eye or the other or both? Do they look normal? Was he running around in a room that he is familiar with or was it a new area to him? Chinchillas do not have good eyesight. If they are unfamiliar with their surroundings, they may appear to be blind. My daughter has a blind chin & she can put her hand in the cage & the chin does not respond what so ever until she actually touches her fur. Of course, if she talks to her, she knows she is there. Her eyes look normal, so I think in this case it is genetic. I know when they have cataracts their eyes are discolored & look like they have a milky substance on them. So, it should be decided by a professional I guess to know for sure. JANE