Difference between revisions of Emmetropia

(5 intermediate revisions by the same user not shown)

Line 1:

{{For|corrective lenses used to get someone to 20/20 vision|20/20 correction}}

'''Emmetropia''' is the state in which an eye is neither [[nearsighted]] nor [[~~farsighted~~]]. 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 free of [[astigmatism]].

'''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==

@@ Line 1: / Line 1: @@
 {{For|corrective lenses used to get someone to 20/20 vision|20/20 correction}}
-'''Emmetropia''' is the state in which an eye is neither [[nearsighted]] nor [[farsighted]]. 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 free of [[astigmatism]].
+'''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==