Emmetropia (from Greek emmetros, "well-proportioned" or "fitting", + -opia) describes the state of vision where a faraway object at infinity is in sharp focus with the crystalline lens in a neutral or...

Astigmatism (from the Greek “a” meaning absence and “stigma” meaning point) is a refractive error (ametropia) that occurs when parallel light rays entering the non accommodating eye do not converge to...

Hyperopia, also termed hypermetropia or farsightedness, is a refractive error in which parallel rays of light entering the eye reach a focal point behind the plane of the retina, while accommodation i...

Myopia is derived from the term "muopia" which, in Greek, means to close the eyes. It manifests itself as blurred distance vision, hence the popular term "short or near-sightedness." Clear distance vi...