There are two phenomena that never cease to amaze me. One is this one: You go through life hearing about Problem X ("migraine headaches are really debilitating!") but you never quite know what the fuss is about. Then you get your first migraine headache and as you're sitting there in the dark feeling nauseous and miserable you suddenly think to yourself "oh, this is what my friends were talking about! Hey, they weren't kidding!"
Every time this happens it somehow takes me by surprise. I guess that, however much you try, you can't easily imagine the actual experience of pain. You have to be shown.
The other phenomenon is that you get used to your own pains, and then find yourself unreasonably surprised that other people don't intuitively understand them. I've worn glasses since I was eight years old, contacts for a couple of decades off and on, and I've been a professional laser scientist (i.e. "someone whose eyes are in chronic danger") so Jacques' story surprises me: You mean other people don't go to the ophthalmologist every year? Oh, right, they probably don't. I only know that intellectually; I don't really remember that from day to day until I read a story like this one.
Human communication, empathy, and imagination are astonishing abilities, but you do discover their limits.