Dirty eyes

Not sure what is causing it but one of Harry's eyes is crusting in one corner. It doesn't bother him and he doesn't mind me cleaning it. I have bathed it with warm water and cotton wool and it just looks dirty, a few hours later it is crusty again. Does anyone have any idea what this is ?

I only have one cat that gets crust around an eye & I normally find it ties in with when he has been sitting out in the pen & it is quite windy so I tend to put it down to that & just bathe as you are doing.If he starts getting a yellow discharge from the inner corners of his eye though I would get him checked in case of infection or if his eyes are red at all then deff.take him along to be seen,eyes are very precious & can soon go wrong.Even if it doesn't look like an infection though remember to always bathe from inside to out & use clean cotton wool each time just in case.