/u/sunagainstgold addressed this in the past a few times, here's the most recent popular thread:
As you might expect, it's likely that myopia was not as prevalent in the past as it is today (although some in that thread may disagree)... but more importantly, lots of manual labor just doesn't require good eyesight in the same way we might expect today (widespread literacy, office work, classrooms, etc.). We probably have different standards for what is considered "good" eyesight. After all, how many people today "don't realize" how bad their eyesight is until they get glasses?
There's also lots of good stuff in there about the ways in which people sought support (both physical and spiritual) for their poor eyesight (and how it was/was not conceived of as a disability).