- A measure of the convergence or divergence of a pair of light rays, defined as the reciprocal of the distance between a point of reference and the point at which the rays intersect.
- The inward or outward turning of one or both eyes that occurs when focusing on an object.
vergence
Dictionary:
ver·gence (vûr'jəns)  |
n.
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Disjunctive movement of the eyes in opposite directions in adjusting to near or far vision; convergence or divergence.
| Wikipedia: Vergence |
For other uses, see Vergence (disambiguation).
A vergence is the simultaneous movement of both eyes in opposite directions to obtain or maintain single binocular vision.[1].
When a creature with binocular vision looks at an object, the eyes must rotate around a vertical axis so that the projection of the image is in the centre of the retina in both eyes. To look at an object closer by, the eyes rotate towards each other (convergence), while for an object farther away they rotate away from each other (divergence). Exaggerated convergence is called cross eyed viewing (focussing on the nose for example) . When looking into the distance, the eyes diverge until parallel, effectively fixating the same point at infinity (or very far away).
Vergence movements are closely connected to accommodation of the eye. Under normal conditions, changing the focus of the eyes to look at an object at a different distance will automatically cause vergence and accommodation.
As opposed to the 500° velocity, convergence movements are far slower, say, 25°. The extraocular muscles may have two types of fiber each with its own nerve supply, hence a dual mechanism.
Vergence dysfunction
A number of vergence dysfunctions exist:[2][3]
- Basic exophoria
- Convergence insufficiency
- Divergence excess
- Basic esophoria
- Convergence excess
- Divergence insufficiency
- Fusional vergence dysfunction
- Vertical phorias
References
- ^ Cassin, B. Dictionary of Eye Terminology. Solomon S.. Gainesville, Fl: Triad Publishing Company. ISBN 0937404683.
- ^ American Optometric Association. Optometric Clinical Practice Guideline: Care of the Patient with Accommodative and Vergence Dysfunction. 1998.
- ^ Duane A. "A new classification of the motor anomalies of the eyes based upon physiological principles, together with their symptoms, diagnosis and treatment." Ann Ophthalmol. Otolaryngol. 5:969.1869;6:94 and 247.1867.
See also
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 | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| Medical Dictionary. The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Read more |
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| Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved. Read more |
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| Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Vergence". Read more |
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