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(Created page with "{{CogPsy}} '''Near vision''' is the vision required to focus on objects less than 2 feet (60cms) from the eye<ref>Coleman,A F (2006). Oxford Dictionary of Psychology, 2nd ...")
 
 
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As an object moves toward the eye, the eye must increase its [[optical power]] to keep the image in focus on the retina. If the power of the cornea and lens is insufficient, as in [[hyperopia]], the image will appear blurred.
 
As an object moves toward the eye, the eye must increase its [[optical power]] to keep the image in focus on the retina. If the power of the cornea and lens is insufficient, as in [[hyperopia]], the image will appear blurred.
   
The [[cilary muscles] in the eye are used to increase the convexity of the eye to aid in near vision.
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The [[refractive index]] of the eye’s lens system allows the eye to produce sharply focused images. For example, geometrical optics show that as a distant object is brought closer to the eye, the focus of the object becomes blurrier in the plane behind the retina; however, as a result of the increase in the refractive power of the eye, this image becomes clear. The refractive power mainly resides in the [[cornea]], but the overall refractive power is achieved by the actual lens changing its shape.<ref>Anon-779080. "Accomodation Reflex." Scribd. N.p., n.d. Web. 24 Oct. 2012. <http://www.scribd.com/doc/4762947/Accomodation-Reflex>.</ref>
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In order to fixate on a near object, the [[ciliary muscle]] contracts around the lens to decrease its size. The [[suspensory ligaments]] relax and the radial tension around the lens is released. This causes the lens to form a more spherical shape achieving a higher level of refractive power.<ref>Anon-779080. "Accomodation Reflex." Scribd. N.p., n.d. Web. 24 Oct. 2012. <http://www.scribd.com/doc/4762947/Accomodation-Reflex>.</ref>
   
 
==See also==
 
==See also==

Latest revision as of 12:10, July 2, 2013

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Near vision is the vision required to focus on objects less than 2 feet (60cms) from the eye[1].

As an object moves toward the eye, the eye must increase its optical power to keep the image in focus on the retina. If the power of the cornea and lens is insufficient, as in hyperopia, the image will appear blurred.

The refractive index of the eye’s lens system allows the eye to produce sharply focused images. For example, geometrical optics show that as a distant object is brought closer to the eye, the focus of the object becomes blurrier in the plane behind the retina; however, as a result of the increase in the refractive power of the eye, this image becomes clear. The refractive power mainly resides in the cornea, but the overall refractive power is achieved by the actual lens changing its shape.[2]

In order to fixate on a near object, the ciliary muscle contracts around the lens to decrease its size. The suspensory ligaments relax and the radial tension around the lens is released. This causes the lens to form a more spherical shape achieving a higher level of refractive power.[3]

See alsoEdit

ReferencesEdit

  1. Coleman,A F (2006). Oxford Dictionary of Psychology, 2nd ed. Oxford:OUP.
  2. Anon-779080. "Accomodation Reflex." Scribd. N.p., n.d. Web. 24 Oct. 2012. <http://www.scribd.com/doc/4762947/Accomodation-Reflex>.
  3. Anon-779080. "Accomodation Reflex." Scribd. N.p., n.d. Web. 24 Oct. 2012. <http://www.scribd.com/doc/4762947/Accomodation-Reflex>.

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