Difference between revisions of Emmetropia
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{{For|corrective lenses used to get someone to 20/20 vision|20/20 correction}} | |||
'''Emmetropia''' is the zero [[refractive state]] in which an eye is neither [[nearsighted]], [[farsighted]], nor [[astigmatism|astigmatic]]. This causes the [[natural focal plane]] to be [[full correction]]. An eye is said to be emmetropic when the image of an object at infinity (parallel light rays) forms on the [[retina]], rather than in front of or behind it, implying it is also free of [[astigmatism]]. | |||
Babies are born [[farsighted]], and become emmetropic over time after birth through [[axial elongation]] during emmetropization. | |||
==Thresholds== | |||
Eyes are generally regarded as emmetropic if their spherical equivalent is between -0.5 and +0.5 D and can achieve 20/20 distance [[visual acuity]] without lenses. | |||
This permits some [[myopia]], [[hyperopia]], and [[astigmatism]]. However, a truly emmetropic eye would typically achieve 20/8 acuity (no myopia or astigmatism) and be blurred to 20/20 through a +0.25 lens (no hyperopia). | |||
==References== | |||
{{reflist}} | |||
[[Category:Articles]] | |||
[[Category:Eye conditions]] | |||