My bantam golden laced Cochin went in to molt recently. She was kind of moping around at first, but we just thought it was a hard molt. When she didn't get better we brought her inside and tried to figure out what was wrong with her. We checked her eyes and her pupils didn't react to light so we decided she was blind, which so far appears to be very accurate. She seems to still be able to see colour but not shapes (she can recognize bright food but can't see hands and runs of tables). We started giving her eye drops, but it didn't seem to affect her very much. Then she started to turn white, the base of her feathers is white. The feather part is white. Basically her under-feathering is totally white. We thought she might have genetic nutritional deficits, which would explain losing colour in her feathers and her deteriorating eyesight, but nothing else seems to be affected. Recently a friend told me that this was happening all over the state (WA state), and that someone who did a necropsy thought it was a more virulent form of Mareks. I've heard of ocular mareks, and her pupils are sort of strange but I can't find white feathers as a symptom and the Cochin doesn't seem to have any of the other symptoms. She walks fine when she wants to, though being blind means she sometimes would rather sit on her heating pad. Her feathers look fine other than being white, and I haven't seen any scabs.
Molting chicken went blind and is now turning white.
Could you post pictures of her eyes? I don't know what is going on with her feathers, but sometimes chickens will feather out differently after a molt. Some breeds don't look like they will end up until the first or second molt. My millefleur bantam this year became much whiter after her molt this fall.
There can be many causes of blindness in chickens besides Mareks disease. Infections, high ammonia levels in the coop air, vitamin A deficiency, avian encephalomyelitis (AE,) fowl pox in the eyes, and cataracts are some of the causes. Here are some good articles to read about eye disorders:
I agree with everything Eggcessive has stated.
I would add that Mareks can effect the feather follicles creating oddities, but usually it is odd growths and bumps, not the feather itself turning white, to my knowledge.
One thing that can cause odd feather regrowth is fenbendazole, which is a wormer, generally sold as Panacur or Safeguard for pigs. Many like to use it for chickens, off label. It can cause weird feather regrowth if it is used during molt.
And, I concur that many chickens change somewhat after the first juvenile or early adult molt, but you won't see a black hen go white unless something is wrong....typically with vitamin/mineral deficiencies.
I'd follow up on the links given by Eggessive to see if there is a deficiency linked with blindness and color loss. I know Vitamin A deficiency can cause trembling, blindness, and paleness.
If anyone is interested or has this problem with there birds:
It turns out she has a common genetic defect, found most famously in a strain of chickens bred for disease testing but also naturally. This defect is a genetic linking of uveitis, which causes blindness and loss of colour in the pupil, and an autoimmune disease causing melanin (the coloring that causes the black colour in feathers and skin) to be lost similar to the human disease (which is actually why they bred the experimental strain).
I hope this helps other people who have this problem.