Emmetropia

Emmetropia

Emmetropia (from the Greek emmetros, "well-proportioned, fitting") describes the state of vision where an object at infinity is in sharp focus with the eye lens in a neutral or relaxed state. This condition of the normal eye focuses rays exactly on the retina resulting in perfect vision. An eye in a state of emmetropia requires no correction.

Emmetropia is a state in which the eye is relaxed and focused on an object more than 6 meters or 20 feet away. The light rays coming from that object are essentially parallel, and the rays are focused on the retina without effort (an emmetropic eye does not need corrective lenses). If the gaze shifts to something closer, light rays from the source are too divergent to be focused without effort. In other words, the eye is automatically focused on things in the distance unless you make an effort to focus elsewhere. For a wild animal or our prehistorical ancestors, this arrangement would be adaptive because it allows for alertness to predators or prey at a distance.

References

* "Anatomy & Physiology: The Unity of Form And Function" by Saladin (4th Edition)
* [http://www.pupileyes.com/index.php?content=emmetropia&lang=english pupilEyes - Learn how Emmetropia happens]


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  • Emmetropia — Em me*tro pi*a ([e^]m m[ e]*tr[=o] p[i^]*[.a]), n. [NL., fr. Gr. e mmetros in measure, proportioned, suitable ( en in + me tron measure) + w ps, wpo s, eye.] (Med.) That refractive condition of the eye in which the rays of light are all brought… …   The Collaborative International Dictionary of English

  • emmetropia — /em:etro pia/ s.f. [comp. del gr. émmetros di giusta misura e opia ]. (med.) [normale capacità visiva] ◀▶ astigmatismo, miopia, presbiopia …   Enciclopedia Italiana

  • emmetropia — [em΄ə trō′pē ə] n. [ModL < Gr emmetros, in measure, fit < en , in + metron, MEASURE + OPIA] the condition of normal refraction of light in the eye, in which vision is perfect emmetropic [em΄əträp′ik] adj …   English World dictionary

  • emmetropia — The state of refraction of the eye in which parallel rays, when the eye is at rest, are focused exactly on the retina. [G. emmetros, according to measure, + ops, eye] * * * em·me·tro·pia .em ə trō pē ə n the normal refractive condition of the eye …   Medical dictionary

  • emmetropia — normalusis regėjimas statusas T sritis fizika atitikmenys: angl. emmetropia; normal vision vok. Emmetropie, f; Normalsichtigkeit, f; Rechtsichtigkeit, f rus. нормальное зрение, n; эмметропия, f pranc. emmétropie, f; vision normale, f …   Fizikos terminų žodynas

  • emmetropia — emmetrope, n. emmetropic /em i trop ik, troh pik/, adj. /em i troh pee euh/, n. Ophthalm. the normal refractive condition of the eye, in which the rays of light are accurately focused on the retina. [1860 65; < NL, equiv. to emmetr (s. of Gk… …   Universalium

  • emmetropia — noun The condition of perfect vision, where images are correctly brought to a focus on the retina …   Wiktionary

  • emmetropia — em·me·tro·pì·a s.f. TS med. normale capacità di rifrazione dell occhio Contrari: ametropia. {{line}} {{/line}} DATA: 1875. ETIMO: comp. del gr. émmetros di giusta misura e di opia …   Dizionario italiano

  • emmetropia — {{hw}}{{emmetropia}}{{/hw}}s. f. Vista normale …   Enciclopedia di italiano

  • emmetropia — pl.f. emmetropie …   Dizionario dei sinonimi e contrari

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