Accommodation reflex

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The accommodation reflex is a reflex action of the eye, in response to focusing on a near object, then looking at distant object (and vice versa), comprising coordinated changes in vergence, lens shape and pupil size. It is dependent on cranial nerve II (afferent limb of reflex), higher centres and cranial nerve III.

A near object (for example, a computer screen) appears large in the 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 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

Light from 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 3rd cranial nerve to the medial rectus muscle.

See also

• Accommodation (eye)
• Ciliary muscle
• Presbyopia

External links

• Accommodation at Georgia State University

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Last updated on Friday May 30, 2008 at 07:13:57 PDT (GMT -0700)
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