Giving him a pair of glasses sounds like the ideal way to go. It tells him that he goofed in a funny way, and is the perfect way to prepare him to be ragged on for years to come! There are tons of things that he might do in the future and you'll be able to hit him with "why aren't you wearing those glasses I got you?", or " do I need to get you another pair of glasses?" All this of course, will only work if he doesn't actually need glasses.