I was talking about emergencies that can’t be taken care of by the person on board, like the two examples I gave. A retinal detachment can result from hitting your head on something, and there’s no way to predict who will get it. If it’s not treated within a few days, you will irreversibly lose your eyesight. I have two friends who had this condition, so it’s not that uncommon. Treatment consists of a delicate operation with lasers done by an eye specialist. If you don’t treat appendicitis right away, you could die.