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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.
Orthoptics is a profession allied to the eye care profession. Orthoptists are the experts in diagnosing and treating defects in eye movements and problems with how the eyes work together, called binocular vision. These can be caused by issues with the muscles around the eyes or defects in the nerves enabling the brain to communicate with the eyes. Orthoptists are responsible for the diagnosis and non-surgical management of strabismus (cross-eyed), amblyopia and eye movement disorders. The word orthoptics comes from the Greek words ὀρθός orthos, "straight" and ὀπτικός optikοs, "relating to sight" and much of the practice of orthoptists concerns disorders of binocular vision and defects of eye movement. Orthoptists are trained professionals who specialize in orthoptic treatment, such as eye patches, eye exercises, prisms or glasses. They commonly work with paediatric patients and also adult patients with neurological conditions such as stroke, brain tumours or multiple sclerosis. With specific training, in some countries orthoptists may be involved in monitoring of some forms of eye disease, such as glaucoma, cataract screening and diabetic retinopathy.
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.
David Hunter Hubel was an American Canadian neurophysiologist noted for his studies of the structure and function of the visual cortex. He was co-recipient with Torsten Wiesel of the 1981 Nobel Prize in Physiology or Medicine, for their discoveries concerning information processing in the visual system. For much of his career, Hubel worked as the Professor of Neurobiology at Johns Hopkins University and Harvard Medical School. In 1978, Hubel and Wiesel were awarded the Louisa Gross Horwitz Prize from Columbia University. In 1983, Hubel received the Golden Plate Award of the American Academy of Achievement.
Pediatric ophthalmology is a sub-speciality of ophthalmology concerned with eye diseases, visual development, and vision care in children.
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.
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 in 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".
Vision therapy (VT), or behavioral optometry, is an umbrella term for alternative medicine treatments using eye exercises, based around the pseudoscientific claim that vision problems are the true underlying cause of learning difficulties, particularly in children. Vision therapy has not been shown to be effective using scientific studies, except for helping with convergence insufficiency. Most claims—for example that the therapy can address neurological, educational, and spatial difficulties—lack supporting evidence. Neither the American Academy of Pediatrics nor the American Academy of Ophthalmology support the use of vision therapy.
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.
The Optometric Extension Program Foundation (OEPF) is an international, non-profit organization dedicated to the advancement of the discipline of optometry, with recent emphasis on behavioral optometry and vision therapy.
Suppression of an eye is a subconscious adaptation by a person's brain to eliminate the symptoms of disorders of binocular vision such as strabismus, convergence insufficiency and aniseikonia. The brain can eliminate double vision by ignoring all or part of the image of one of the eyes. The area of a person's visual field that is suppressed is called the suppression scotoma. Suppression can lead to amblyopia.
Stereoblindness is the inability to see in 3D using stereopsis, or stereo vision, resulting in an inability to perceive stereoscopic depth by combining and comparing images from the two eyes.
A vision disorder is an impairment of the sense of vision.
The Mind's Eye is a 2010 book by neurologist Oliver Sacks. The book contains case studies of people whose ability to navigate the world visually and communicate with others have been compromised, including the author's own experience with cancer of the eye and his lifelong inability to recognise faces.
Monocular deprivation is an experimental technique used by neuroscientists to study central nervous system plasticity. Generally, one of an animal's eyes is sutured shut during a period of high cortical plasticity. This manipulation serves as an animal model for amblyopia, a permanent deficit in visual sensation not due to abnormalities in the eye.
Stereopsis recovery, also recovery from stereoblindness, is the phenomenon of a stereoblind person gaining partial or full ability of stereo vision (stereopsis).
Frederick W. Brock (1899–1972), born in Switzerland, was an optometrist, a major contributor to vision therapy, and the inventor of various vision therapy devices including the Brock string. Brock's approach to treating eye disorders was crucial in paving the way to overcoming an erroneous but long-standing medical consensus that stereopsis could not be acquired in adulthood but only during a critical period early in life: neuroscientist Susan R. Barry, the first person to have received widespread media attention for having acquired stereo vision in adulthood, attributes him a central role in her recovery of stereopsis, a discovery which in turn influenced the prevalent scientific conceptions with regard to the neuroplasticity of the visual system.
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.
References
- 1 2 Sacks, Oliver (June 12, 2006). "Stereo Sue". The New Yorker . ISSN 0028-792X . Retrieved April 3, 2018.
- ↑ "Susan Barry". Mount Holyoke College. January 29, 2016. Archived from the original on April 2, 2012. Retrieved April 3, 2018.
- ↑ "The Man Who Forgot How to Read and Other Stories, Summer 2011, imagine... - BBC One". BBC. Retrieved September 2, 2019.
- 1 2 "Susan Barry - Meribeth E. Cameron Faculty Award for Scholarship". Mount Holyoke College. March 5, 2013. Archived from the original on August 21, 2020. Retrieved July 23, 2013.
- ↑ "Eyes on the Brain". Psychology Today. Retrieved March 15, 2018.
- ↑ Barry, Susan (May 16, 2011). "Were You Nervous? Watching My Husband Blast Off Into Space". Psychology Today. Retrieved March 15, 2018.
- ↑ S. Barry: Fixing my Gaze, 2009, pages 30–31
- ↑ S. Barry: Fixing my Gaze, 2009, page 46
- ↑ S. Barry: Fixing my Gaze, 2009, pages 60 and 65
- ↑ Barry, Susan (April 14, 2012). "Fixing My Gaze - Video". bigthink.com.
- ↑ Fixing my gaze, bigthink.com (transcript)
- ↑ "Bio | Stereo Sue | Stereo Sue". www.stereosue.com. Archived from the original on January 15, 2020. Retrieved April 3, 2018.
- 1 2 S. Barry: Fixing my Gaze, 2009, pages 138-140
- ↑ S. Barry: Fixing my Gaze, 2009, page 147
- ↑ Peck, Morgen (July 19, 2012). "How a movie changed one man's vision forever" . Retrieved April 3, 2018.
- ↑ "How 'Hugo' Gave One Neuroscientist the Gift of Stereo-Vision". bsandrew.blogspot.de. March 19, 2012. Retrieved April 3, 2018.
- ↑ Barry, Susan R. (2009) Fixing My Gaze: A Scientist's Journey into Seeing in Three Dimensions. New York: Basic Books. ISBN 978-0-465-00913-8
- ↑ Barry, Susan R. (2021). Coming to Our Senses: A Boy Who Learned to See, A Girl Who Learned to Hear, and How We All Discover the World. New York: Basic Books. ISBN 978-1-5416-7515-5. OCLC 1199127175.
- ↑ Barry, Susan R. (2024). Dear Oliver: An Unexpected Friendship with Oliver Sacks. New York: The Experiment. ISBN 9781891011306. OCLC 1390775551.
