Not really. Refractive error are generally the result of optical imperfections in the lens and cornea and are not directly affected by diet. Certainly, in extreme cases deficiencies in vitamins or dry eye can affect the refraction but in general, refractive errors are intrinsic to the eye.
No. Hyperopia or myopia is complex -- genetic with environmental effects (lots of near work worsens myopia during formative years).
No. There is no evidence that a special diet will prevent or correct refractive errors.