the white sclera of my cat''s eye is halfway over her eye,what is causing this?
The white part of the eye I believe you're referring to, is your cat's 'third eyelid', or nictating membrane. When this is halfway across the eye, it usually indicates either a specific eye problem, or general illness in the body. An evaluation by the vet, would be your best course of action at this time, to get a definite diagnosis after a hands-on exam. There is a condition called 'toro virus' which may also cause this symptom.
I hope your cat will be fine, once she's diagnosed and treated by the vet!