"oriented. There are three types of skew deviations: Type 1: Upward deviation of both eyes; sound-induced vestibular symptoms; both eyes show counterclockwise rotary upward rotation Type 2: Hypertropia in one eye; dorsolateral medullary infarctions; excyclotropia in the ipsilateral eye; hypertropia in the contralateral eye Type 3: Simultaneous hypertropia one eye and hypotropia in the other eye; upper brainstem lesion Conway M (2013) Oculomotor disorders in the brainstem, Supranuclear palsies [City University London] Skew deviation Skew deviation is an unusual ocular deviation (strabismus), wherein the eyes move upward (hypertropia), but in opposite directions. Skew deviation is caused by abnormal prenuclear vestibular"
"Diplopia Diplopia, commonly known as double vision, is the simultaneous perception of two images of a single object that may be displaced horizontally, vertically, diagonally (i.e., both vertically and horizontally), or rotationally in relation to each other. It is usually the result of impaired function of the extraocular muscles (EOMs), where both eyes are still functional but they cannot turn to target the desired object. Problems with EOMs may be due to mechanical problems, disorders of the neuromuscular junction, disorders of the cranial nerves (III, IV, and VI) that stimulate the muscles, and occasionally disorders involving the supranuclear oculomotor pathways"
"Heterophoria Heterophoria is an eye condition in which the directions that the eyes are pointing at rest position, when ""not"" performing binocular fusion, are not the same as each other, or, ""not straight"". There can be esophoria, where the eyes tend to cross inward in the absence of fusion; exophoria, in which they diverge; or hyperphoria, in which one eye points up or down relative to the other. Phorias are known as 'latent squint' because the tendency of the eyes to deviate is kept latent by fusion. A person with two normal eyes has single vision (usually) because of the"
"Strabismus Strabismus, is a condition in which the eyes do not properly align with each other when looking at an object. The eye which is focused on 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 loss of depth perception. If onset is during adulthood, it is more likely to result in double vision. Strabismus can occur due to muscle dysfunction, farsightedness, problems in the brain, trauma, or infections. Risk factors include premature birth, cerebral palsy, and a family history of the condition."
"for two eyes not looking in the same direction) is in fact Duane syndrome. Fissure changes, and the other associated characteristics of Duane's such as up or down shoots and globe retraction, are also vital when deciding whether any abduction limitation is the result of Duane's and not a consequence of VI or abducens cranial nerve palsy. Acquired Duane's syndrome is a rare event occurring after peripheral nerve palsy. The majority of patients remain symptom free and able to maintain binocularity with only a slight face turn. Amblyopia is uncommon and, where present, rarely dense. This can be treated with"
"Cyclotropia Cyclotropia is a form of strabismus in which, compared to the correct positioning of the eyes, there is a torsion of one eye (or both) about the eye's visual axis. Consequently, the visual fields of the two eyes appear tilted relative to each other. The corresponding ""latent"" condition – a condition in which torsion occurs only in the absence of appropriate visual stimuli – is called cyclophoria. Cyclotropia is often associated with other disorders of strabism, can result in double vision, and can cause other symptoms, in particular head tilt. In some cases, subjective and objective cyclodeviation may result"
"Esotropia 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"
"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 horizontal axis so that the projection of the image is in the centre of the retina in both eyes. To look at an object closer by, 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"
"have ""ametropia"" or be ""ametropic"". This eye cannot focus parallel rays of light (light from distant objects) on the retina, or needs accommodation to do so. The word ""ametropia"" can be used interchangeably with ""refractive error"". Types of ametropia include myopia, hyperopia and astigmatism. They are frequently categorized as spherical errors and cylindrical errors: There is evidence to suggest genetic predilection for refractive error. Individuals that have parents with certain refractive errors are more likely to have similar refractive errors. The Online Mendelian Inheritance in Man (OMIM) database has listed 261 genetic disorders in which myopia is one of the"
"either of the eyes can be seen to deviate. Alternation of the strabismus may occur spontaneously, with or without subjective awareness of the alternation. Alternation may also be triggered by various tests during an eye exam. Unilateral strabismus has been observed to result from a severe or traumatic injury to the affected eye. Horizontal deviations are classified into two varieties. ""Eso"" describes inward or convergent deviations towards the midline. ""Exo"" describes outward or divergent misalignment. Vertical deviations are also classified into two varieties. ""Hyper"" is the term for an eye whose gaze is directed higher than the fellow eye while"
"One and a half syndrome The one and a half syndrome is a rare weakness in eye movement affecting both eyes, in which one cannot move laterally at all, and the other can move in only one lateral direction (inward or outward). More formally, it is characterized by """"a conjugate horizontal gaze palsy in one direction and an internuclear ophthalmoplegia in the other"""". The most common manifestation of this unusual syndrome is limitation of horizontal eye movement to abduction (moving away from the midline) of one eye (e.g. right eye in the diagram on the right) with no horizontal movement"
"Hypertropia Hypertropia is a condition of misalignment of the eyes (strabismus), whereby the visual axis of one eye is higher than the fellow fixating eye. Hypotropia is the similar condition, focus being on the eye with the visual axis lower than the fellow fixating eye. Dissociated Vertical Deviation is a special type of hypertropia leading to slow upward drift of one or rarely both eyes, usually when the patient is inattentive. Refractive errors such as hyperopia and Anisometropia may be associated abnormalities found in patients with vertical strabismus. The vertical miscoordination between the two eyes may lead to Hypertropia may"
"from an early ventral simultanagnosia/pure alexia"". Simultanagnosia Simultanagnosia (or simultagnosia) is a rare neurological disorder characterized by the inability of an individual to perceive more than a single object at a time. This type of visual attention problem is one of three major components (the others being optic ataxia and optic apraxia) of Bálint's syndrome, an uncommon and incompletely understood variety of severe neuropsychological impairments involving space representation (visuospatial processing). The term ""simultanagnosia"" was first coined in 1924 by Wolpert to describe a condition where the affected individual could see individual details of a complex scene but failed to grasp"
"Monocular vision Monocular vision is vision in which both eyes are used separately. By using the eyes in this way, as opposed by binocular vision, the field of view is increased, while depth perception is limited. The eyes of an animal with monocular vision are usually positioned on opposite sides of the animal's head, giving it the ability to see two objects at once. The word monocular comes from the Greek root, ""mono"" for single, and the Latin root, ""oculus"" for eye. Monocular vision impairment refers to having no vision in one eye with adequate vision in the other. Monopsia"
"Astigmatism (optical systems) An optical system with astigmatism is one where rays that propagate in two perpendicular planes have different foci. If an optical system with astigmatism is used to form an image of a cross, the vertical and horizontal lines will be in sharp focus at two different distances. The term comes from the Greek α- (""a-"") meaning ""without"" and στίγμα (""stigma""), ""a mark, spot, puncture"". There are two distinct forms of astigmatism. The first is a third-order aberration, which occurs for objects (or parts of objects) away from the optical axis. This form of aberration occurs even when"
"Far-sightedness Far-sightedness, also known as hyperopia, is a condition of the eye in which light is focused behind, instead of on, the retina. This results in close objects appearing blurry, while far objects may appear normal. As the condition worsens, objects at all distances may be blurry. Other symptoms may include headaches and eye strain. People may also experience accommodative dysfunction, binocular dysfunction, amblyopia, and strabismus. The cause is an imperfection of the eyes. Often it occurs when the eyeball is too short, or the lens or cornea is misshapen. Risk factors include a family history of the condition, diabetes,"
"Convergence insufficiency Convergence insufficiency or convergence disorder is a sensory and neuromuscular anomaly of the binocular vision system, characterized by a reduced ability of the eyes to turn towards each other, or sustain convergence. 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 sufferers. Note that some Internet"
"Hering–Hillebrand deviation The Hering–Hillebrand deviation describes the mismatch between the theoretical and empirical horopterThe horopter is the set of points that projects at the same location in the two retinae (i.e. that have the same visual direction). Geometrically the horopter is a circle passing through the nodal point of the two eyes and through the fixation point. This is known as the horizontal geometrical horopter, or as the Vieth–Müller circle. This is the set of points that correspond ""geometrically"" to the intersection between visual lines at identical eccentricities. There is also a vertical horopter which the a straight line on"
"Horror fusionis In ophthalmology, horror fusionis is a condition in which the eyes have an unsteady deviation, with the extraocular muscles performing spasm-like movements that continuously shift the eyes away from the position in which they would be directed to the same point in space, giving rise to diplopia. Even when the double vision images are made to nearly overlap using optical means such as prisms, the irregular movements prevent binocular fusion. The name ""horror fusionis"" (Latin phrase literally meaning ""fear of fusion"") arises from the notion that the brain is, or at least appears to be, actively preventing binocular"
"Oculogyric crisis Oculogyric crisis (OGC) is the name of a dystonic reaction to certain drugs or medical conditions characterized by a prolonged involuntary upward deviation of the eyes. The term ""oculogyric"" refers to the bilateral elevation of the visual gaze, but several other responses are associated with the crisis. Epilepsy can manifest as oculogyric seizures, also called versive seizures. Initial symptoms include restlessness, agitation, malaise, or a fixed stare. Then comes the more characteristically described extreme and sustained upward deviation of the eyes. In addition, the eyes may converge, deviate upward and laterally, or deviate downward. The most frequently reported"
"Internuclear ophthalmoplegia Internuclear ophthalmoplegia (INO) is a disorder of conjugate lateral gaze in which the affected eye shows impairment of adduction. When an attempt is made to gaze contralaterally (relative to the affected eye), the affected eye adducts minimally, if at all. The contralateral eye abducts, however with nystagmus. Additionally, the divergence of the eyes leads to horizontal diplopia. That is, if the right eye is affected the patient will ""see double"" when looking to the left, seeing two images side-by-side. Convergence is generally preserved. The disorder is caused by injury or dysfunction in the medial longitudinal fasciculus (MLF), a"
"Conjugate gaze palsy Conjugate gaze palsies are neurological disorders affecting the ability to move both eyes in the same direction. These palsies can affect gaze in a horizontal, upward, or downward direction. These entities overlap with ophthalmoparesis and ophthalmoplegia. Symptoms of conjugate gaze palsies include the impairment of gaze in various directions and different types of movement, depending on the type of gaze palsy. Signs of a person with a gaze palsy may be frequent movement of the head instead of the eyes. For example, a person with a horizontal saccadic palsy may jerk their head around while watching a"
"Skew deviation Skew deviation is an unusual ocular deviation (strabismus), wherein the eyes move upward (hypertropia), but in opposite directions. Skew deviation is caused by abnormal prenuclear vestibular input to the ocular motor nuclei, most commonly due to brainstem or cerebellar stroke. Other causes include multiple sclerosis and head trauma. Skew deviation is usually characterized by torticollis (head tilting) and binocular torsion. The exact pathophysiology of skew deviation remains incompletely understood. Skew deviation appears to be a perturbation of the ocular tilt reaction, which is itself probably a vestigial righting response used to keep fish and other lateral-eyed animals properly"
"Amblyopia Amblyopia, also called lazy eye, is a disorder of sight due to the eye and brain not working well together. It results in decreased vision in an eye that otherwise typically appears normal. It is the most common cause of decreased vision in a single eye among children and younger adults. The cause of amblyopia can be any condition that interferes with focusing during early childhood. This can occur from poor alignment of the eyes, an eye being irregularly shaped such that focusing is difficult, one eye being more nearsighted or farsighted than the other, or clouding of the"
"coming from the same object (but each passing through a different hole) are diffracted back toward the eye and onto different places on the retina. This leads to double vision (objects having doubled edges) around the rim of each hole the eye is not focussing on, which can make the overall image disturbing and tiring to look at for prolonged periods of time. Unlike conventional prescription glasses, pinhole glasses produce an image without the pincushion effect around the edges (which makes straight lines appear curved). While pinhole glasses are claimed to be useful for people who are both near- and"
"human eye. As the two images captured by each eye is incompatible for stereo processing, they fight for visual dominance over the other eye's side view, resulting in alternating views from the two eyes, where the non-dominant view is almost unseen. This effect often occurs when wearing a monocular HMD. In this setup, researchers also observed objects that completely vanish for several seconds from user’s attention. Describes the phenomenon when both eyes perceive different images that are overlapping, but the brain is not able to distinguish between those. This phenomenon is also known as the inability for visual separation. Describes"
"do not suppress may display a certain type of spasm-like irregular movement of the eyes in the vicinity of the fixation point (see: Horror fusionis). Diplopia can also occur when viewing with only one eye; this is called monocular diplopia, or, where the patient perceives more than two images, monocular polyopia. While there rarely may be serious causes behind monocular diplopia symptoms, this is much less often the case than with binocular diplopia. The differential diagnosis of multiple image perception includes the consideration of such conditions as corneal surface keratoconus, subluxation of the lens, a structural defect within the eye,"
"above and below it which would be affected by shear of retinal correspondence points. 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. 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. Listing's law, however, does not account for all cyclorotations. In particular, in the presence of cyclodisparity (that is, when two images"
"Refractive error Refractive error, also known as refraction error, is a problem with focusing light accurately onto the retina due to the shape of the eye. The most common types of refractive error are near-sightedness, far-sightedness, astigmatism, and presbyopia. Near-sightedness results in far away objects being blurry, far-sightedness and presbyopia result in close objects being blurry, astigmatism causes objects to appear stretched out or blurry. Other symptoms may include double vision, headaches, and eye strain. Near-sightedness is due to the length of the eyeball being too long, far-sightedness the eyeball too short, astigmatism the cornea being the wrong shape, and"
"isometropia, amblyogenic unilateral or bilateral astigmatism, image degradation. When the covered eye is the non-amblyopic eye, the amblyopic eye suddenly becomes the person's only means of seeing. The strabismus is revealed by the movement of that eye to fixate on the examiner's finger. There are also vertical tropias (hypertropia and hypotropia) and cyclotropias. Binocular vision anomalies include: diplopia (double vision), visual confusion (the perception of two different images superimposed onto the same space), suppression (where the brain ignores all or part of one eye's visual field), horror fusionis (an active avoidance of fusion by eye misalignment), and anomalous retinal correspondence"
"that tungsten spectral energy influences the convergence which can also show an impact on reading and near visual tasks because of its brightness and miosis. Prolonged reading and working under this lighting can cause convergence disorders and visual fatigue 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 number of vergence dysfunctions exist: As a further type of dysfunction there is evidence for a link between a vergence abnormality in which there"
"from an eye through a process called visual development. Development may be interrupted by strabismus if the child always fixates with one eye and rarely or never fixates with the other. To avoid double vision, the signal from the deviated eye is suppressed, and the constant suppression of one eye causes a failure of the visual development in that eye. Also, amblyopia may cause strabismus. If a great difference in clarity occurs between the images from the right and left eyes, input may be insufficient to correctly reposition the eyes. Other causes of a visual difference between right and left"
"gazing in the direction contralateral to the affected eye. One and a half syndrome: “One and a half syndrome” also affects horizontal gaze. One eye is completely incapable of horizontal movement, while the other eye is capable of horizontal movement only in one direction away from the midline. Conjugate eye movement Conjugate eye movement refers to motor coordination of the eyes that allows for bilateral fixation on a single object. A conjugate eye movement is a movement of both eyes in the same direction to maintain binocular gaze (also referred to as “yoked” eye movement). This is in contrast to"