I agree with
@Eggcessive. That looks like ocular Marek's disease to me also. I've had three birds with it.
Too late to do anything preventative, unfortunately that Genie is out of the bottle and it ain't gonna fit back in. All birds have been exposed. Not all will develop OMD. Some may develop symptoms of the other forms of MD. Time will tell.
In the mean time as long as she is comfortable, eating, etc I'd put her back with her flock mates. She may be sensitive to light as in light may cause her eye pain. What she has is the equivalent of a human having a herpes infection in their eye called uveitis. It will cause blindness and pain in the eye so keeping her in shade or unlit areas will help her a lot.
My birds with OMD never went out in the sun but stuck to shaded areas and the coop and did well for about a year to 18 months after developing symptoms. Then they lost weight and developed neurological problems that resembled a stroke.
I'm so sorry but you are not alone. Like recommended, I would have a necropsy done on one of your birds when the time comes but in the mean time if I were you, until I had a solid diagnosis I would close my flock no birds in no birds out and see what happens next.
I was lucky in that my husband is a retired eye doctor and he was able to use a hand held microscope on one of my affected birds and give me a diagnosis.
