Probably is conjunctivitus and needs a vet to administer eye medications for a few days. They use the same stuff that people use. Be careful and don't rub you hands near your eyes - conjunctivitus is contagious between cats and people.
Call your vet or emergency vet and describe the eye in detail, especially if there's swelling or he's light sensitive. And be ready to take him in to the vet for an exam. Good luck - hope it's nothing, but I'm one for being safe than sorry.
I'm very prone to pink eye and had done some research about passing it to my cat and what I had found, as well as was told on here by many people, was that you CANNOT pass pink eye between you and your cat... I would still get him to the vet to find out what's going on... pink eye is usually accompanied by icky pussing from the affected eye as well... I've had pink eye a few times since getting Oliver and he's always super attached to me (well he's a mama's boy anyway) when I'm sick and he never has gotten pink eye... I never did actually ask my vet about it though - maybe you could ask yours and give us a definitive answer about it passing between cats and people....
i was gonna say! i get pink eye ALL the freaking time and ive NEVER given it to either of my kitties - ive given it to my mom and some of my coworkers and probably some of my customers (hey theyre the ones who INSIST i come to work at a fast food place with it LOL)
...but never my cats
From what I remember reading when I was looking into it, was the only other species that it can be transferred to from humans was pigs.... it was a few years ago that I had asked/looked into this, so I have no idea now where I read this and/or who on here had mentioned that...