Explanation

Myopia is nearsightedness: the eye focuses distant objects in front of the retina, so distant objects appear blurred while near objects are clear; it is corrected with concave lenses. Farsightedness (hypermetropia) is the opposite condition, while cataract is a clouding of the lens and presbyopia is age-related loss of accommodation. It is corrected with concave (diverging) lenses, which shift the focus back onto the retina.