Possibly blind chicken, does this sound like Marek's?

I noticed this EE hen acting a little "off" two or three days ago and have been watching her closely. By "off" I mean she has not been as active as the others, has been hanging back at scratch time, self-isolating, low energy. She's molting, is about two years old. Her eyes seem unusually dark, as if the pupils are fully dilated. Today she couldn't seem to locate the gate to go out. So after they all roosted DH and I went out and checked her out. On shining a light into her eyes, the pupil refected back grey, almost opaque white. Other chickens' pupils shine black and normal. Her eye does not look deformed, keyhole shaped, but the pupil did not contract from the light. We isolated her and will conduct further tests in the morning: crop, belly, swelling, weight, etc. Thoughts? The flock is isolated as to other chickens. Thanks.