View source for Accommodation reflex

{{unreferenced|date=August 2009}}
The '''accommodation reflex''' is a [[reflex action]] of the [[eye]], in response to [[focus (optics)|focusing]] on a near object, then looking at distant object (and vice versa),   comprising coordinated changes in [[vergence]], [[lens (anatomy)|lens]] shape and [[pupil]] size. It is dependent on [[optic nerve|cranial nerve II]] ([[afferent limb]] of reflex), higher centres and [[oculomotor nerve|cranial nerve III]].

[[Image:Focus in an eye.svg|thumb|right|Light from a single point of a distant object and light from a single point of a near object being brought to a focus.]]
A near object (for example, a computer screen) appears large in the [[field of view|field of vision]], and the eye receives [[light]] from wide angles. When moving focus from a distant to a near object, the eyes converge. The [[ciliary muscle]] contracts making the [[lens (anatomy)|lens]] more convex, shortening its focal length. The [[pupil]] constricts in order to prevent diverging light rays from hitting the periphery of the [[retina]] and resulting in a blurred image.  

==Pathway==
Information from the light on each retina is taken to the [[occipital lobe]] via the [[optic nerve]] and [[optic radiation]], where it is interpreted as vision. The [[peristriate area 19]] interprets accommodation, and sends signals via the [[Edinger-Westphal nucleus]] and the [[Oculomotor nerve|3rd cranial nerve]] to the [[ciliary muscle]], the medial rectus muscle and (via parasympathetic fibres) the [[sphincter pupillae muscle]].<ref>Bhatnagar SC. Neuroscience for the study of communicative disorders. p 185-6. | http://books.google.com/books?id=d0D0ghp2fSAC&pg=PA185&lpg=PA185&dq=accommodation+reflex+cranial+nerve+iii&source=bl&ots=JWF1lLVjYt&sig=-rQh6t8JPfSUapV8yiIvBuBcqNw&hl=en&ei=02_LS4ftEsP-8Ab60NX8BA&sa=X&oi=book_result&ct=result&resnum=10&ved=0CC4Q6AEwCQ#v=onepage&q=accommodation%20reflex%20cranial%20nerve%20iii&f=false</ref>.

==See also==
*[[Accommodation (eye)]]
*[[Ciliary muscle]]
*[[Presbyopia]]

==References==
{{Reflist}}

==External links==
*[http://hyperphysics.phy-astr.gsu.edu/hbase/vision/accom.html Accommodation] at [[Georgia State University]]

*{{MeshName|Ocular+Accommodation}}
{{reflex}}

[[Category:Cranial nerves]]
[[Category:Eye]]
[[Category:Ophthalmology]]
[[Category:Reflexes]]

{{Neuroscience-stub}}

[[tr:Akomodasyon refleksi]]
[[uk:Акомодація ока]]
[[Category:2Fix]]