My son's had the same symptoms as you've described, but I couldn't see anything in it. Just before I was going to take him to the doctor's, I bought some Optrex drops for itchy and irritated eyes, thinking that there might be an eyelash stuck where it couldn't be seen and the drops might flush it out. As it happened, he'd scratched his cornea - very faintly - but that's what'd caused all the stinging and redness. he was given some ointment to put in his eye, and the problem cleared up very quickly.