ametropia


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Related to ametropia: astigmatism, myopia

ametropia

 [am″ĕ-tro´pe-ah]
an ocular disorder in which parallel rays fail to come to a focus on the retina. adj., adj ametrop´ic.

am·e·tro·pi·a

(am-ĕ-trō'pē-ă), Do not confuse this word with emmetropia.
An optic condition in which an error of refraction occurs such that with the eye at rest the retina is not in conjugate focus with light rays from distant objects, that is, only less distant objects are focused on the retina.
[G. ametros, disproportionate, fr. a- priv. + metron, measure, + ōps, eye]

ametropia

/am·e·tro·pia/ (am″ĕ-tro´pe-ah) a condition of the eye in which images fail to come to a proper focus on the retina, due to a discrepancy between the size and refractive powers of the eye.ametrop´ic

ametropia

(ăm′ĭ-trō′pē-ə)
n.
An eye abnormality, such as nearsightedness, farsightedness, or astigmatism, resulting from faulty refractive ability of the eye.

am′e·trop′ic (-trŏp′ĭk, -trō′pĭk) adj.

ametropia

[am′itrō′pē·ə]
Etymology: Gk, ametros, irregular, opsis, sight
a condition characterized by an optic defect involving an error of refraction, such as astigmatism, hyperopia, or myopia. ametropic, adj.

am·e·tro·pia

(am'ĕ-trō'pē-ă)
The optic condition in which there is an error of refraction so that with the eye at rest the retina is not in conjugate focus with light rays from distant objects, i.e., only less distant objects are focused on the retina.
[G. ametros, disproportionate, fr. a- priv. + metron, measure, + ōps, eye]

ametropia

Any deviation, in the relaxed focus of the eye, from the normal state in which distant objects form sharp and clear images on the RETINA. Ametropia may take the form of HYPERMETROPIA, MYOPIA or the meridional visual defect ASTIGMATISM. The state of normal refraction is called emmetropia.

ametropia 

Anomaly of the refractive state of the eye in which, with relaxed accommodation, the image of objects at infinity is not formed on the retina. Thus vision may be blurred. The ametropias are: astigmatism, hyperopia (hypermetropia) and myopia. The absence of ametropia is called emmetropia. Syn. refractive error; error of refraction; refraction (although not strictly correct since this term may also refer to the lack of ametropia). See hyperopic defocus; myopic defocus; refraction; refractive error; biological-statistical theory; emmetropization theory; nativistic theory.
axial ametropia Ametropia due primarily to an abnormal length of the eye while the refractive power is approximately normal (Fig. A8).
refractive ametropia Ametropia due primarily to an abnormal refractive power of the eye while the length is approximately normal. Refractive ametropias can be attributed to either an abnormal radius of curvature of the surfaces of the cornea, or the crystalline lens (curvature ametropia) or to an abnormal index of refraction of one or more of the ocular media (index ametropia).
Fig. A8 Emmetropia E, axial hyperopia H and axial myopia M. In emmetropia, parallel rays are focused on the retina. In hyperopia, the eye is relatively too short and the principal focus is behind the retinaenlarge picture
Fig. A8 Emmetropia E, axial hyperopia H and axial myopia M. In emmetropia, parallel rays are focused on the retina. In hyperopia, the eye is relatively too short and the principal focus is behind the retina

ametropia

the state when the image of a distant object is not in focus on the retina; due usually to some defect in the refraction of the optic system of the eye.
References in periodicals archive ?
Terminology Explanation Spectacle refraction The spherical and cylindrical combination required, at a stated vertex distance, to correct the patient's ametropia Ocular refraction The spectacle refraction adjusted by compensating for the back vertex distance (BVD) Spectacle astigmatism Can occur either from corneal and/or lenticular astigmatism.
49) Practitioners should also remember that cycloplegic drugs might temporarily modify the structures of anterior chamber, inducing astigmatism or modifying an existing astigmatic ametropia.
Further evidence for the active nature of emmetropisation comes from the observation that, for both spherical refractive errors and astigmatism, the greater the degree of ametropia at birth, the faster the growth tends towards emmetropia.
The event at Leicester City FC's Walkers Stadium on May 23 will include: occupational therapist Elaine Cowley discussing how a childhood in front of the TV is detrimental to development; former BCLA president Martin Lloyd speaking on the overlap between a sports science graduate and a Sportvision practitioner; and researcher Angela Egan will exclusively reveal the findings of her study on how uncorrected ametropia in one eye can effect performance in a game of rugby.
Piggyback lenses are normally used where an RGP is indicated but cannot be tolerated by the patient or is inclined to decentre eg, scarred corneas, high astigmatic ametropia and ectatic disorders such as keratoconus and pellucid marginal degeneration.
Another option using rigid lenses and open to those with levels of moderate ametropia and limited astigmatism is orthokeratology (see article 4 in these series).
This article discusses contact lens options for patients with high ametropia (over [+ or -] 10.