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The reflex, controlled by the parasympathetic nervous system, involves three responses: pupil constriction, lens accommodation, and convergence. A near object (for example, a computer screen) subtends a large area in the visual field, i.e. the eyes receive light from wide angles.
In optometry, convergence is the simultaneous inward movement of both eyes toward each other, usually in an effort to maintain single binocular vision when viewing an object. [6] This is the only eye movement that is not conjugate, but instead adducts the eye. [7]
if R < 1, the series converges absolutely; if r > 1, the series diverges; or equivalently if. | a n + 1 a n | > 1 {\displaystyle \left| {\frac {a_ {n+1}} {a_ {n}}}\right|>1} for all large n (regardless of the value of r ), the series also diverges; this is because. | a n | {\displaystyle |a_ {n}|}
Convergence insufficiency is characterized by one or more of the following diagnostic findings: patient symptoms, high exophoria at near, reduced accommodative convergence / accommodation ratio, receded near point of convergence, and low fusional vergence ranges and/or facility.
This is also known as the nth root test or Cauchy's criterion . Let. r = lim sup n → ∞ | a n | n , {\displaystyle r=\limsup _ {n\to \infty } {\sqrt [ {n}] {|a_ {n}|}},} where. lim sup {\displaystyle \limsup } denotes the limit superior (possibly. ∞ {\displaystyle \infty } ; if the limit exists it is the same value).
Vergence-accommodation conflict ( VAC ), also known as accommodation-vergence conflict, is a visual phenomenon that occurs when the brain receives mismatching cues between vergence and accommodation of the eye. This commonly occurs in virtual reality devices, augmented reality devices, 3D movies, and other types of stereoscopic displays and ...
Depth perception is the ability to perceive distance to objects in the world using the visual system and visual perception. It is a major factor in perceiving the world in three dimensions. Depth perception happens primarily due to stereopsis and accommodation of the eye .
The term "binocular disparity" refers to geometric measurements made external to the eye. The disparity of the images on the actual retina depends on factors internal to the eye, especially the location of the nodal points, even if the cross section of the retina is a perfect circle. Disparity on retina conforms to binocular disparity when ...
Since the Howard-Dolman test described above is cumbersome, stereoacuity is usually measured using a stereogram in which separate panels are shown to each eye by superimposing them in a stereoscope using prisms or goggles with color or polarizing filters or alternating occlusion. [3] A good procedure is a chart, analogous to the familiar Snellen visual acuity chart, in which one letter in each ...
A Brock string (named after Frederick W. Brock) is an instrument used in vision therapy. It consists of a white string of approximately 10 feet in length with three small wooden beads of different colors. The Brock string is commonly employed during treatment of convergence insufficiency and other anomalies of binocular vision.