Making a diagnosis requires a vet looking at the eye.
As far as helping the eye for temporary relief...you can rinse the eye with human saline, to flush out irritants or foreign material. You can place sterile eye lubricant (drugstore) in the eye to help keep the surface of the cornea protected. There is no over the counter medication for the eye that you can use in your cats eye without an appropriate diagnosis...so you can treat for another couple days and see if the eye responds...but I always recommend seeing a vet!
Dr.V
__________________
Dr. D.A. Vamvakias
Veterinarian