Question about my Cat's eye?

My cat's eye isn't opening. (she is a barn kitty, outside all the time) Usually, in the morning, she has goop in her eyes. Even from the time she was an indoor kitty. I usually pick it out. This morning, though, one of her eyes was shut. It had a little goop on it. I wasn't sure if she was scratched in her eye by another animal, or if it shut because of the goop. I opened it halfway, and it looks fine. Should I open it the rest of the way? do you think it was the goop? If so, should I use a wet wash cloth just like to open a human's eye with pink eye?