I don't have much experience dealing with this sort of thing, either. In my poultry book, it says to test for blindness slowly move your finger towards the bird's eye. If they blink, they are not blind. You have to do it slowly and straight at the eye... if you disturb the air, even a blind bird will blink. To test for pupil reactivity, just grab a flashlight. A normal pupil will get larger when it is in shadow and get smaller when a light is shined in it.
I don't think there is a cure or even a treatment for Marek's disease. (If that's what this is!) Many people will cull affected birds at the first sign because it is highly contagious. There is a vaccine available, but I don't know anything about administering it. It may be worth it to get some professional advice. When one of my birds was sick I contacted the "chicken doctor" Peter Brown at First State Veterinary Supply. He is not a vet, but has degrees in poultry science and tons of experience. A consultation is $25, but if you need any medication he will apply the $25 towards that. I was very impressed with his service.
http://www.firststatevetsupply.com/ None of the vets around me will treat chickens, so this worked out well.
I would suggest searching the forum and internet for marek's disease and reading all you can about it. Also, if you could tell us more about Linda and the rest of your flock it might help some of the more experienced members help you. For example, has her eye always been weird? If not, when did you notice the change? Does she "miss" when she pecks at stuff? Is she still eating, drinking, laying and pooping normally? How many birds do you have, are any others sick in any way, have any died recently? Have you separated Linda from the rest of the flock? (A good idea when illness is suspected!) Just a few things off the top of my head!
