DS4 had 20/30 vision, and his reading has improved dramatically (as in from not doing it at all to choosing to do it!) since he saw the developmental optometrist and got reading glasses.
I suspected a problem beyond the far-sightedness, since he loved books but avoided looking at them when we read them. (And he's a very visual kid.) The DO found "some visual immaturity" when he examined him, so there were some issues there. But the glasses did help him, absolutely. There's more to reading than how far away you can see things, and no one reads books from across the room, like an eye chart is. Those basic eye tests are pretty useless for reading readiness, IMHO.