I've noticed lately that my 1 1/2 year old has a faint grey line across the iris of each of his eyes. It appears to be on the outermost surface of the eye, and is faint to see. I can try to take a photograph tomorrow in the daylight, but it may be difficult. No one else has noticed it except for me. His vision doesn't seem to be affected, we do agility classes and he has zero issues navigating a course. I just hadn't noticed it before when he was younger and am a little worried it could be "something".