In many cases of thiamine deficiency (Goat Polio) recovery of eyesight in total or at least part is possible. That's why I'm sort of hoping this is the cause.
10 mg per kg (or 2.2 lbs). So a 24 lb goat should be getting 109 mg thiamine (prescribed).
Check this link out to find out more about treatment and details. It's also a great place for overall care, even though they tend to focus on meat goats.
http://www.jackmauldin.com/health/goat_polio.htm
It sounds like you're taking excellent care, but there is always the chance that something IN the food has caused a drain in her levels (could be mold that you can't see).
More than anything I hope this can be resolved - however, even if can't, with proper precautions put in place for her safety and comfort, this goat can enjoy a good life.
If you close a question, you can reopen it at any time rather than re-post, but any way you want to do this is fine.
I'm also going to ask around for other input on this, so hang in there ok?
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One of the other experts here has suggested that pregnancy be ruled out as a causation.
Sometimes, a vitamin A deficiency and/or hypertension brought on by the pregnancy can effect vision.
Is there any chance she's pregnant?