Vergence

in a classic stereogram A vergence is the simultaneous movement of both eyes in opposite directions to obtain or maintain single binocular vision. When a creature with binocular vision looks at an object, each eye rotates 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, the eyes rotate towards each other (convergence), while for an object farther away, they rotate away from each other (divergence) until the lines of sight for the eyes are parallel. Exaggerated convergence is called cross eyed viewing (focusing on the nose, for example) . When looking into the distance, the eyes diverge until parallel, effectively fixating on the same point at infinity (or very far away). Vergence is closely connected to accommodation of the eye. Under normal visual conditions, looking at an object at a different distance will automatically cause changes in both vergence and accommodation, sometimes known as the accommodation-convergence reflex. When under non-typical visual conditions, like when looking at a stereogram, the vergence and accommodation of the eyes will not match, resulting in the viewer experiencing the vergence-accommodation conflict. As opposed to the 500°/s velocity of saccade movements, vergence movements are far slower, around 25°/s.…

in a classic stereogram A vergence is the simultaneous movement of both eyes in opposite directions to obtain or maintain single binocular vision. When a creature with binocular vision looks at an object, each eye rotates 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, the eyes rotate towards each other (convergence), while for an object farther away, they rotate away from each other (divergence) until the lines of sight for the eyes are parallel. Exaggerated convergence is called cross eyed viewing (focusing on the nose, for example) . When looking into the distance, the eyes diverge until parallel, effectively fixating on the same point at infinity (or very far away). Vergence is closely connected to accommodation of the eye. Under normal visual conditions, looking at an object at a different distance will automatically cause changes in both vergence and accommodation, sometimes known as the accommodation-convergence reflex. When under non-typical visual conditions, like when looking at a stereogram, the vergence and accommodation of the eyes will not match, resulting in the viewer experiencing the vergence-accommodation conflict. As opposed to the 500°/s velocity of saccade movements, vergence movements are far slower, around 25°/s. The extraocular muscles may have two types of fiber each with its own nerve supply, hence a dual mechanism. ===Divergence=== In ophthalmology, divergence is the simultaneous outward movement of both eyes away from each other, usually in an effort to maintain single binocular vision when viewing an object. It is a type of vergence eye movement. A divergence of the eyes in the vertical direction is physiologically seen during a head tilt, due to vestibular signaling, and when viewing a rotating visual image. While the visual system is generally poor at adjusting to the acceleration of visual motion, this vertical divergence has proven more adaptable, possibly being caused by a visually induced activation of the vestibular nuclei, which usually convey information from the accelerometers of the inner ear. ==See also== Cyclovergence Duction Version (eye) Autostereogram Eye examination Orthoptist Vergence-Accommodation Conflict ==References==

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