Anatomy & Physiology
Emmetropia & Ametropia

Emmetropia Light comes to focus directly on the retina when accommodation is relaxed. No corrective lenses are need for distance viewing.
Myopia Or �nearsighted.� Light comes to focus in front of the retina requiring corrective lenses.	Hyperopia Or �farsighted�. Light comes to focus behind the retina often requiring corrective lenses.

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When accommodation is at rest, the emmetropic eye is capable of bringing images of a distant object to focus on the retina. In optics, a distant object is one which is twenty feet or more from the eye (optical infinity). All the other conditions shown on this page are forms of ametropia. A relatively young hyperope with a mild correction may be capable of bringing light to focus on the retina without eyeglasses or contact lenses. The additional plus power needed can be acquired through accommodation. In the case of the myope, however, even the slightest refractive error needs to be corrected with spectacles or contact lenses in order to achieve sharp vision under all lighting conditions.