It took centuries to get to disposable contact lenses while trying to figure out the physics, both in optics and in manufacturing any sort of spectacles, at the same time.
Will the survivors of the apocalypse be able to pick up where we left off or will they essentially start from scratch? That depends on the apocalypse and on the survivors. Do documents and knowledge survive, perhaps in a stash or in digital form? Do the survivors include an optician or a material engineer? Chances look good if that's the case. If no, life will get a lot harder for many people.
I'm not a geneticist, I don't even play one on TV. But i'm fairly confident in saying: evening out? That's not how this works. When your daddy's sperm combined with your mother's egg, a whole host of chance processes happened to make up your genes. It's random as far as I can tell. It isn't just averaging out between them.