The pupil looks dilated and large, and many chickens with blindness have dilated pupils to let more light in. The iris appears light colored. What does the other eye look like?
The iris of the eye may turn gray, and the pupil can become irregular and small. Pictures of the eyes are welcome. You can ask your vet if they can send blood off to a lab for a pcr test Mareks, and in the meantime call and ask RAL about how to go about testing. Tell them you have a vet who may...
Here is where you can contact for Mareks testing:
https://www.vetdna.com/application/forms/aviansubmittalform.pdf
If you should lose her eventually, your state vet lab may do a necropsy where they can do further testing. Here is a list of state vet labs:
https://www.metzerfarms.com/poultry-labs.html