D.B.
Did he notice this before going to the doctor? It could be that the slit lamp (I think they call it that) that shines SO bright in his eyes after he is dialated might be causing it.
Wait a few days and then assess him again. If he says it's still there, call that doctor back up and tell him, IF he's an opthamologist. If he's an optomitrist, I agree with CA - get him into an opthamologist.
Dawn