My 5 year old half ancona, half silkie rooster seemed to suddenly go blind about 6 weeks ago. No noted injury or infection. He can find the food and water inside his coop so he still is healthy. He crows every morning, responds when I go near him, and generally seems happy. (Although he occasionally runs into things in the coop and he is not allowed to free range anymore.) He cannot navigate the perch inside the enclosed pen but can only make it up the ramp (and sometimes has to have help with that.) He lives with 2 hens who seem unaffected. Does this just happen and now i have a handicapped rooster or are chickens suseptible to some disease that I am unaware of? I've researched Merck's, but I don't think he has this. Any ideas?