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Esotropia is a form of strabismus in which one or both eyes turns inward. The condition can be constantly present, or occur intermittently, and can give the affected individual a "cross-eyed" appearance. It is the opposite of exotropia and usually involves more severe axis deviation than esophoria. Esotropia is sometimes erroneously called "lazy eye", which describes the condition of amblyopia; a reduction in vision of one or both eyes that is not the result of any pathology of the eye and cannot be resolved by the use of corrective lenses. Amblyopia can, however, arise as a result of esotropia occurring in childhood: In order to relieve symptoms of diplopia or double vision, the child's brain will ignore or "suppress" the image from the esotropic eye, which when allowed to continue untreated will lead to the development of amblyopia. Treatment options for esotropia include glasses to correct refractive errors, the use of prisms, orthoptic exercises, or eye muscle surgery. The term is from Greek eso meaning "inward" and trope meaning "a turning".
In biology, binocular vision is a type of vision in which an animal has two eyes capable of facing the same direction to perceive a single three-dimensional image of its surroundings. Binocular vision does not typically refer to vision where an animal has eyes on opposite sides of its head and shares no field of view between them, like in some animals.
Stereoscopy is a technique for creating or enhancing the illusion of depth in an image by means of stereopsis for binocular vision. The word stereoscopy derives from Greek στερεός (stereos) 'firm, solid', and σκοπέω (skopeō) 'to look, to see'. Any stereoscopic image is called a stereogram. Originally, stereogram referred to a pair of stereo images which could be viewed using a stereoscope.
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.
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.
Strabismus is a vision 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.
Amblyopia, also called lazy eye, is a disorder of sight in which the brain fails to fully process input from one eye and over time favors the other eye. It results in decreased vision in an eye that typically appears normal in other aspects. Amblyopia is the most common cause of decreased vision in a single eye among children and younger adults.
A 3D display is a display device capable of conveying depth to the viewer. Many 3D displays are stereoscopic displays, which produce a basic 3D effect by means of stereopsis, but can cause eye strain and visual fatigue. Newer 3D displays such as holographic and light field displays produce a more realistic 3D effect by combining stereopsis and accurate focal length for the displayed content. Newer 3D displays in this manner cause less visual fatigue than classical stereoscopic displays.
Random-dot stereogram (RDS) is stereo pair of images of random dots which, when viewed with the aid of a stereoscope, or with the eyes focused on a point in front of or behind the images, produces a sensation of depth, with objects appearing to be in front of or behind the display level.
Cyclopean image is a single mental image of a scene created by the brain through the process of combining two images received from both eyes. The mental process behind the Cyclopean image is crucial to stereo vision. Autostereograms take advantage of this process in order to trick the brain to form an apparent Cyclopean image from seemingly random patterns. These random patterns appear often in daily life such as in art, children's books, and architecture.
Stereopsis is the component of depth perception retrieved through binocular vision. Stereopsis is not the only contributor to depth perception, but it is a major one. Binocular vision happens because each eye receives a different image because they are in slightly different positions on one's head. These positional differences are referred to as "horizontal disparities" or, more generally, "binocular disparities". Disparities are processed in the visual cortex of the brain to yield depth perception. While binocular disparities are naturally present when viewing a real three-dimensional scene with two eyes, they can also be simulated by artificially presenting two different images separately to each eye using a method called stereoscopy. The perception of depth in such cases is also referred to as "stereoscopic depth".
Exotropia is a form of strabismus where the eyes are deviated outward. It is the opposite of esotropia and usually involves more severe axis deviation than exophoria. People with exotropia often experience crossed diplopia. Intermittent exotropia is a fairly common condition. "Sensory exotropia" occurs in the presence of poor vision in one eye. Infantile exotropia is seen during the first year of life, and is less common than "essential exotropia" which usually becomes apparent several years later.
Infantile esotropia is an ocular condition of early onset in which one or either eye turns inward. It is a specific sub-type of esotropia and has been a subject of much debate amongst ophthalmologists with regard to its naming, diagnostic features, and treatment.
Stereoscopic acuity, also stereoacuity, is the smallest detectable depth difference that can be seen in binocular vision.
The health effects of 3D are the aspects in which the human body is altered after the exposure of three-dimensional (3D) graphics. These health effects typically only occur when viewing stereoscopic, autostereoscopic, and multiscopic displays. Newer types of 3D displays like light field or holographic displays do not cause the same health effects. The viewing of 3D stereoscopic stimuli can cause symptoms related to vision disorders that the individual already had, as a person with a healthy binocular vision shouldn't experience any side effects under three-dimensional exposure.
Cyclodisparity refers to the difference in the rotation angle of an object or scene viewed by the left and right eyes. Cyclodisparity can result from the eyes' torsional rotation (cyclorotation) or can be created artificially by presenting to the eyes two images that need to be rotated relative to each other for binocular fusion to take place.
Stereopsis recovery, also recovery from stereoblindness, is the phenomenon of a stereoblind person gaining partial or full ability of stereo vision (stereopsis).
Binocular neurons are neurons in the visual system that assist in the creation of stereopsis from binocular disparity. They have been found in the primary visual cortex where the initial stage of binocular convergence begins. Binocular neurons receive inputs from both the right and left eyes and integrate the signals together to create a perception of depth.
Stereoscopic motion, as introduced by Béla Julesz in his book Foundations of Cyclopean Perception of 1971, is a translational motion of figure boundaries defined by changes in binocular disparity over time in a real-life 3D scene, a 3D film or other stereoscopic scene. This translational motion gives rise to a mental representation of three dimensional motion created in the brain on the basis of the binocular motion stimuli. Whereas the motion stimuli as presented to the eyes have a different direction for each eye, the stereoscopic motion is perceived as yet another direction on the basis of the views of both eyes taken together. Stereoscopic motion, as it is perceived by the brain, is also referred to as cyclopean motion, and the processing of visual input that takes place in the visual system relating to stereoscopic motion is called stereoscopic motion processing.
Visual impairment in art is a limited topic covered by research, with its focus being on how visually impaired people are represented in artwork throughout history. This is commonly portrayed through the inclusion of objects such as canes and dogs to symbolize blindness, which is the most frequently depicted visual impairment in art. Many notable figures in art history, such as Leonardo da Vinci, Claude Monet, and Georgia O'Keeffe, were visually impaired, or theorized to be so.
References
- ↑ Christa M. van Mierlo; Eli Brenner; Jeroen B.J. Smeets (2011). "Better performance with two eyes than with one in stereo-blind subjects' judgments of motion in depth". Vision Research. 51 (11): 1249–1253. doi:10.1016/j.visres.2011.03.015. PMID 21458479. S2CID 615787.
- ↑ Jeremy M. Wolfe; Richard Held (March 1980). "Cyclopean stimulation can influence sensations of self-motion in normal and stereoblind subjects". Perception & Psychophysics. 28 (2): 139–142. doi: 10.3758/bf03204339 . PMID 7432987.
- ↑ Marmor M. F., Shaikh S., Livingstone M. S., Conway B. R., Livingstone MS, Conway BR (September 2004). "Was Rembrandt stereoblind?". N. Engl. J. Med. 351 (12): 1264–5. doi:10.1056/NEJM200409163511224. PMC 2634283 . PMID 15371590.
- ↑ Rembrandt (van Rijn)
- ↑ New York Times: A defect that may lead to a masterpiece (June 13, 2011)
- ↑ "The Man Who Forgot How to Read and Other Stories", BBC accessed 30 June 2011
- ↑ Murphy, John. "Eye to Eye with Dr. Oliver Sacks" Archived 2013-04-19 at the Wayback Machine , Review of Optometry, 9 December 2010
- ↑ Peck, Morgen (2012-07-19). "How a movie changed one man's vision forever". BBC News. Retrieved July 20, 2012.