Bad Eyesight and Evolution
Remi.b and Potterbond007 have put forward excellent answers. Would like to add something..

One of the reasons that Myopia (near sightedness) happens is because of use of eye in work like reading, which requires working with close objects. I don't think there was much working with close objects in the past. So very few people with myopia might have been present (and of course, they may have had disadvantages in catching prey.)

Other common disease is hypermetropia which generally occurs during old age, past the reproductive prime, so it could not have much evolutionary impact.