When does age-related farsightedness usually start?
An elderly eyeball is one that can't see things close up. That's why this word means farsightedness. But this is the kind of farsightedness that only comes with age. So you have to be an elderly oldey to have 老眼.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.