Most people who are short-sighted could confirm that it’s surprisingly hard to notice what you can’t see. I found out I needed glasses as a teenager. My aunt was telling me about getting glasses for the first time, and what a surprise it had been to see the world in detail. She hadn’t realised it was possible to, say, make out the individual leaves on trees. She thought everyone only saw a blur of green foliage, as in a child’s drawing of a tree. We were in the garden. “Wait, what?” I said, mind-blown. “When you look at that tree there, you can see the leaves?”