Take it to the vet. Eye problems can get very bad very quickly, and you could end up with a blind cat. Make sure they stain the eye to look for abrasions or ulcers before they give you any eye medication. There are meds out there that if they are put into an eye with an injury, it can make it worse, not better.

Eye discharge can be caused by anything from illness like a cold, an injury, or even a tumor.