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Vergence
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, 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, 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'' (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 movements are 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- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Divergence (eye)
A vergence is the simultaneous eye movement (sensory), movement of both eyes in opposite directions to obtain or maintain single binocular vision. 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, the eyes rotate towards each other (#Convergence, convergence), while for an object farther away, they rotate away from each other (#Divergence, divergence). 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 movements are closely connected to accommodation (eye), 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Divergence
In vector calculus, divergence is a vector operator that operates on a vector field, producing a scalar field giving the rate that the vector field alters the volume in an infinitesimal neighborhood of each point. (In 2D this "volume" refers to area.) More precisely, the divergence at a point is the rate that the flow of the vector field modifies a volume about the point ''in the limit'', as a small volume shrinks down to the point. As an example, consider air as it is heated or cooled. The velocity of the air at each point defines a vector field. While air is heated in a region, it expands in all directions, and thus the velocity field points outward from that region. The divergence of the velocity field in that region would thus have a positive value. While the air is cooled and thus contracting, the divergence of the velocity has a negative value. Physical interpretation of divergence In physical terms, the divergence of a vector field is the extent to which the vector fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convergence
Convergence may refer to: Arts and media Literature *''Convergence'' (book series), edited by Ruth Nanda Anshen *Convergence (comics), "Convergence" (comics), two separate story lines published by DC Comics: **A four-part crossover storyline that united the four Weirdoverse titles in 1997 **A 2015 crossover storyline spanning the Multiverse (DC Comics), DC Comics Multiverse *Convergence (journal), ''Convergence'' (journal), an academic journal that covers the fields of communications and media *Convergence (novel), ''Convergence'' (novel), by Charles Sheffield *Convergence (Cherryh novel), ''Convergence'' (Cherryh novel), by C. J. Cherryh Music *Convergence (Front Line Assembly album), ''Convergence'' (Front Line Assembly album), 1988 *Convergence (David Arkenstone and David Lanz album), ''Convergence'' (David Arkenstone and David Lanz album), 1996 *Convergence (Dave Douglas album), ''Convergence'' (Dave Douglas album), 1999 *Convergence (Warren Wolf album), ''Convergence'' (Warre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convergence Insufficiency
Convergence insufficiency is a sensory and neuromuscular anomaly of the binocular vision system, characterized by a reduced ability of the Human eyes, eyes to turn towards each other, or sustain Convergence (eye), convergence. Symptoms The symptoms and signs associated with convergence insufficiency are related to prolonged, visually demanding, near-centered tasks. They may include, but are not limited to, diplopia (double vision), asthenopia (eye strain), transient blurred vision, difficulty sustaining near-visual function, abnormal fatigue, headache, and abnormal postural adaptation, among others. In some cases, difficulty with making eye contact have been noted as a complaint amongst those affected. Note that some Internet resources confuse convergence and divergence dysfunction, reversing them. Diagnosis Diagnosis of convergence insufficiency is made by an eye care professional skilled in binocular vision dysfunctions, such as an optometrist, ophthalmologist, or Orthoptics, or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autostereogram
An autostereogram is a two-dimensional (2D) image that can create the optical illusion of a three-dimensional (3D) scene. Autostereograms use only one image to accomplish the effect while normal stereograms require two. The 3D scene in an autostereogram is often unrecognizable until it is viewed properly, unlike typical stereograms. Viewing any kind of stereogram properly may cause the viewer to experience vergence-accommodation conflict. The optical illusion of an autostereogram is one of depth perception and involves stereopsis: depth perception arising from the different perspective each eye has of a three-dimensional scene, called binocular parallax. Individuals with disordered binocular vision and who cannot perceive depth may require a wiggle stereogram to achieve a similar effect. The simplest type of autostereogram consists of a horizontally repeating pattern, with small changes throughout, that looks like wallpaper. When viewed with proper vergence, the repeating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binocular Vision
Binocular vision is seeing with two eyes. The Field_of_view, field of view that can be surveyed with two eyes is greater than with one eye. To the extent that the visual fields of the two eyes overlap, #Depth, binocular depth can be perceived. This allows objects to be recognized more quickly, camouflage to be detected, spatial relationships to be perceived more quickly and accurately (#Stereopsis, stereopsis) and perception to be less susceptible to optical illusions, optical illusions. In secion #Medical, Medical attention is paid to the occurrence, defects and sharpness of binocular vision. In section #Biological, Biological the occurrence of binocular vision in animals is described. Geometric terms When the left eye (LE) and the right eye (RE) observe two objects X and Y, the following concepts are important:Krol J.D.(1982),"Perceptual ghosts in stereopsis, a ghosly problem in binocular vision", PhD thesis ISBN 90-9000382-7.Koenderink J.J.;van Doorn A.J. (1976) "Geometry of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vergence-accommodation Conflict
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 autostereoscopic displays. The effect can be unpleasant and cause eye strain. Two main ocular responses can be distinguished: vergence of eyes, and accommodation. Both of these mechanisms are crucial in stereoscopic vision. Vergence or independent inward/outward rotation of eyes is engaged to fixate on objects and perceive them as single. Incorrect vergence response can cause double vision. Accommodation is the eye’s focusing mechanism and it is engaged to produce a sharp image on a retina. Both of these mechanisms are neurally linked forming the accommodation-convergence reflex of eyes. One can distinguish vergence a distance of a point t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclovergence
Cyclovergence is the simultaneous occurring cyclorotation (torsional movement) of both eyes which is performed in opposite directions to obtain or maintain single binocular vision. Normal cyclovergence and cycloversion Conjugate cyclorotations of the eye (that is, cyclorotations in the same direction) are called ''cycloversion''. They mainly occur due to Listing's law, which, under normal circumstances, constrains the cyclorotation in dependence on the vertical and horizontal movements of the eye. Visually evoked cyclovergence Listing's law, however, does not account for all cyclorotations. In particular, in the presence of cyclodisparity (that is, when two images are presented which would need to be rotated in relation to each other in order to allow visual fusion to take place), the eyes perform cyclovergence, rotating around their gaze directions in opposite directions, as a motor response to cyclodisparity. Such additional, visually evoked cyclovergence appears to superi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convergence Micropsia
Convergence micropsia is a type of micropsia characterized by the reduction in apparent size of objects viewed when the eyes are more converged than they need to be for the distance of the object from the eyes. It occurs mainly during stereoscopy and when viewing autostereograms (such as Magic Eye pictures). In these cases, the object is depicted by the two half images of a stereogram or by the contents of the autostereogram. Moving the stereogram or the autostereogram closer to the eyes increases convergence of the eyes and reduces the apparent size of the depicted object. If a correctly arranged stereogram or autostereogram is viewed with crossed eyes, then the depicted objects will appear smaller than if it is viewed with eyes diverged or parallel. Convergence micropsia could also occur if one looked at the world through base-out prisms. Explanation Apparent size is influenced by the size of the retinal image of an object and by its apparent distance from the eyes. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Divergence Excess
Strabismus is an eye disorder in which the eyes do not properly align with each other when looking at an object. The eye that is pointed at an object can alternate. The condition may be present occasionally or constantly. If present during a large part of childhood, it may result in amblyopia, or lazy eyes, and loss of depth perception. If onset is during adulthood, it is more likely to result in double vision. Strabismus can occur out of muscle dysfunction (e.g., myasthenia gravis), farsightedness, problems in the brain, trauma, or infections. Risk factors include premature birth, cerebral palsy, and a family history of the condition. Types include esotropia, where the eyes are crossed ("cross eyed"); exotropia, where the eyes diverge ("lazy eyed" or "wall eyed"); and hypertropia or hypotropia, where they are vertically misaligned. They can also be classified by whether the problem is present in all directions a person looks (comitant) or varies by direction (incomitant) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Accommodation (eye)
Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image or focus (optics), focus on an object as its distance varies. In this, distances vary for individuals from the far point—the maximum distance from the eye for which a clear image of an object can be seen, to the near point—the minimum distance for a clear image. Accommodation usually acts like a reflex, including part of the accommodation-convergence reflex, but it can also be consciously controlled. The main ways animals may change focus are: * Changing the shape of the lens. * Changing the position of the lens relative to the retina. * Changing the axial length of the eyeball. * Changing the shape of the cornea. Focusing mechanisms Focusing the light scattered by objects in a three dimensional environment into a two dimensional collection of individual bright points of light requires the light to be bent. To get a good image of these points of light on a defined area re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
