Materiały źródłowe

• #1 Strabismus – StatPearls – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK560782/

  Etiopathogenesis of strabismus is unclear. The physiology of ocular motility involves extraocular muscles, cranial nerves, supranuclear pathways, and their cerebral controls. All of these have been implicated in the development of strabismus. The following 2 theories are popular: […] Claude Worth’s theory states that an inherent absence of cortical fusional potential is the cause of strabismus. […] Chavasse theory states that motor alignment leads to a poor sensory status, which, if left untreated, leads to strabismus. This theory justifies early treatment for squint, which leads to sustained improvement in binocular single vision (BSV). Hence, many surgeons justify doing early surgery in conditions like infantile esotropia.

• #2 Infantile Esotropia – EyeWiki

  https://eyewiki.org/Infantile_Esotropia

  Infantile esotropia is a form of ocular motility disorder in which there is an inward turning of one or both eyes, commonly referred to as „crossed eyes”. […] The etiology of infantile esotropia is unknown. Many theories have been postulated regarding the pathogenesis of the disease. The Worth theory suggests that there is an irreparable congenital defect in the infant’s visual system and that surgery can be carried out at leisure mostly for cosmetic purposes. On the other hand, Chavasse suggested a primary motor dysfunction, where the associated poor fusion and lack of high-grade stereopsis is probably a sensory adaptation to abnormal visual stimulation during early binocular development caused by the motor misalignment. Thus, surgical correction should be performed early during infancy.

• #3

  https://link.springer.com/article/10.1007/s00417-022-05935-9

  Strabismus is not a condition in itself but the consequence of an underlying problem. […] A small percentage of all strabismus cases are the consequence of well-described genetic syndromes, acquired insult, or disease affecting the extraocular muscles (EOMs) or their innervations. […] However, in most strabismus cases, that is comitant, non-restrictive, non-paralytic strabismus, the EOMs and their innervations function properly. […] They are generally believed to be caused by deficits in the central neural pathways involved in visual perception and oculomotor control. […] The goal of this narrative review is to discuss the possible causes behind this particular type of eye misalignment and to raise awareness among eyecare professionals about the important role the central nervous system plays in strabismus etiology, and the subsequent implications regarding its treatment.

• #4

  https://link.springer.com/article/10.1007/s00417-022-05935-9

  The aim of this study was to review and discuss the latest evidence about the etiology of the most common, and at the same time, the less known, types of ocular deviations: non-restrictive, non-paralytic, and developmental strabismus. […] The idea that concomitant, non-paralytic, developmental strabismus are caused by deficits in the central nervous system is supported by different arguments. […] The higher-than-average prevalence of strabismus in the presence of CNS defects indicates that in many cases, the cause of strabismus lies in the brain. […] More subtle, covert neurological deficits could be the cause of strabismus in a much larger proportion of cases. […] The concept of strabismic control is another important point indicating central origin and central relevance in strabismus.

• #5 Strabismus – Wikipedia

  https://en.wikipedia.org/wiki/Strabismus

  The extraocular muscles control the position of the eyes. Thus, a problem with the muscles or the nerves controlling them can cause paralytic strabismus. The extraocular muscles are controlled by cranial nerves III, IV, and VI. An impairment of cranial nerve III causes the associated eye to deviate down and out and may or may not affect the size of the pupil. Impairment of cranial nerve IV, which can be congenital, causes the associated eye to drift up and perhaps slightly inward. Sixth nerve palsy causes the associated eye to deviate inward and has many causes due to the relatively long path of the nerve. Increased cranial pressure can compress the nerve as it runs between the clivus and brain stem. […] Evidence indicates a cause for strabismus may lie with the input provided to the visual cortex.

• #5 Strabismus – Wikipedia

  https://en.wikipedia.org/wiki/Strabismus

  Amblyopia may also 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 eyes, such as asymmetrical cataracts, refractive error, or other eye disease, can also cause or worsen strabismus.

• #6 Strabismus (Squint) | Ento Key

  https://entokey.com/strabismus-squint/

  In incomitant strabismus, the efferent pathway is defective. […] The restriction of eye movements may be caused by neurogenic or mechanical factors. […] In incomitant strabismus, the affected eye gets deviated. The magnitude of deviation (angle of deviation) depends on the degree of paralysis and the direction in which the patient is looking. […] In paretic squint, the amount of innervation flowing to both eyes is always determined by the fixating eye. Therefore, the angle of deviation depends on which eye is used for fixation.

• #6 Strabismus (Squint) | Ento Key

  https://entokey.com/strabismus-squint/

  Heterophoria and Heterotropia […] In comitant strabismus, primary deviation is equal to secondary deviation and ocular deviation is equal in all directions of gaze. […] In comitant strabismus, the efferent pathways are normal and, thus, retain their coordination. Either the afferent path is defective (usually due to poor visual acuity) or the central mechanism mediating fixation and fusional reflexes is underdeveloped. […] Defects in central mechanisms mediating fixation and fusional reflexes can lead to comitant strabismus. […] The following factors are contributory in the etiology of comitant strabismus: Genetics. Defective vision in one eye: It may result due to anisometropia or opacities in the media (corneal opacity or congenital cataract). It causes the affected eye to lose fixation and subsequently deviate. Muscular imbalance: The congenital or developmental defects of extraocular muscles (EOMs) may result in muscular imbalance.

• #7 Strabismus (Squint) Classification and Management

  https://patient.info/doctor/strabismus-squint

  Strabismus often occurs in children who are otherwise completely normal. However, children with disorders that affect the brain such as cerebral palsy, Down’s syndrome, hydrocephalus and space-occupying lesions are more likely to develop strabismus. […] Stroke is the leading cause of strabismus in adults. Neurological problems and Graves’ disease (thyroid eye disorders) are common causes. Trauma may also cause strabismus through damage to the oculomotor cortex and nerves or through direct damage to the muscles of the orbit. […] The pathophysiology is most easily considered by examining non-paralytic and paralytic squint separately. […] Non-paralytic, concomitant squint is usually congenital. Affected children have full movement in both eyes if tested separately and extraocular muscles and nerves are grossly normal. There is no diplopia and the angle between the longitudinal axes of the eyes remains constant on testing eye movement.

• #7 Strabismus (Squint) Classification and Management

  https://patient.info/doctor/strabismus-squint

  Paralytic squint is usually acquired through damage to the extraocular muscles or their nerves. Diplopia is usual and maximal in the direction of gaze produced by the weak muscle. The angle between the longitudinal axes of the eyes varies through the range of eye movements. […] The III, IV and VI cranial nerves are involved. A nerve palsy may be isolated or there may be multiple nerves involved. Each nerve may be affected at any point along its course from the brainstem to the orbit. Myopathies may give rise to diplopia and restriction of eye movement; in severe cases there may be a degree of paralytic squint.

• #8

  https://journals.lww.com/ijo/fulltext/2017/65030/what_s_new_for_us_in_strabismus_.3.aspx

  Our understanding regarding the etiopathogenesis of strabismus is continually being revised. […] Recent advances in imaging techniques and advances in the field of genetics have remarkably changed the recent-day understanding. The advent of high-resolution magnetic resonance imaging (MRI) has led to the discovery of extraocular muscle pulleys which are the condensation of the connective tissue of the posterior Tenon’s fascia. These help in maintaining the paths of the extraocular muscles. Pulley heterotropia or abnormalities can lead to the development of strabismus. Instability of the rectus pulleys has been shown to be associated with incomitant strabismus. […] Genetic basis of strabismus is also being explored. A recent study by Altick et al. has shown through microarray analysis that the gene expression in the extraocular muscles of the strabismic and the nonstrabismic individuals. They found that 25% of the muscle-specific genes were downregulated in the extraocular muscles of strabismic patients.

• #9 Squint, or strabismus: Causes and treatment

  https://www.medicalnewstoday.com/articles/220429

  A squint is when a persons eyes do not align properly but look in different directions. […] This usually occurs because the muscles that control the movement of the eye and the eyelid, the extraocular muscles, are not working together. […] It can also happen from an injury or disorder to the brain means which impacts the eyes ability to work together. […] Constant strabismus makes binocular vision impossible, which causes a person to lose depth perception. […] Strabismus can be congenital, meaning a person is born with it. […] High amounts of hyperopic refractive error can make the affected eye turn inward, in an attempt to better focus. […] Hydrocephalus can also lead to strabismus. Hydrocephalus is a condition in which too much cerebrospinal fluid builds up in and around the brain.

• #10 Refractive Errors and Concomitant Strabismus: A Systematic Review and Meta-analysis | Scientific Reports

  https://www.nature.com/articles/srep35177

  The pathogenesis of different types of concomitant strabismus has not been well established. […] The exact mechanism of how myopia may lead to exotropia is not certain. We postulated that the fusional control at distant of myopes is weakened due to the blurred distant vision. […] Our results revealed a very strong association between hyperopia and esotropia in a dose-related effect manner. […] This dose-related effect is highly relevant to public health. […] Anisometropia was found to be associated with strabismus and both esotropia and exotropia based on pooled unadjusted ORs. […] However, the pooled adjusted OR did not support the association of anisometropia with exotropia and esotropia. Therefore, there is still no definite conclusion on their relationship and further studies are required to confirm the association.

• #11

  https://lupinepublishers.com/ophthalmology-journal/fulltext/neural-mechanisms-and-causes-of-Non-Traumatic-and-Non-Pathological-strabismus.ID.000162.php

  Strabismus alters various brain areas the neural synapses and connections of which are affected. […] However, the mechanisms and causes of strabismus remain under investigation. The reason for this is because strabismus is a condition that presents a multifarious and multi-level complexity. […] Consequently, it appears that visual disparity and eye alignment are closely intertwined. More precisely, the interruption of this interaction between visual disparity and eye alignment might be attributed as one of the causes of strabismus which is produced by abnormal sensory experiences early in life. […] The absence of sensory fusion and the abnormal development of binocular neurons of disparity, will eventually lead to the loss of critical error signals in the cortex or the brain stem, necessary for the orthoptic alignment and development of the eyes.

• #12

  https://lupinepublishers.com/ophthalmology-journal/fulltext/neural-mechanisms-and-causes-of-Non-Traumatic-and-Non-Pathological-strabismus.ID.000162.php

  This may result in poor visual activity and stimuli in the early months of life. Moreover, this condition once developed may further lead to false calibration of the neural circuits and connections in multiple levels from the visual cortex to the motor neurons. […] The sensitivity of the binocular vision neurons and the binocular motor coordination of the eyes are connected with the level of development of the visual system through relevant visual experience in early stages of an individuals life. […] The degree that the visual and visuomotor function may be influenced, due to the aforementioned early abnormal visual experience, depends largely on the age of onset, the duration and the type of interruption. […] The ocular dominant columns in layer 4 of the visual cortex which develop through the visual input of each eye separately will be unavoidably affected.

• #13 Squint – Zero To Finals

  https://zerotofinals.com/paediatrics/neurology/squint/

  Squint refers to misalignment of the eyes. It is is also known as strabismus. When the eyes are not aligned, the images on the retina do not match and the person will experience double vision. […] When this occurs in childhood, before the eyes have fully established their connections with the brain, the brain will cope with this misalignment by reducing the signal from the less dominant eye. This results in one eye they use to see (the dominant eye) and one eye they ignore (the “lazy eye”). If this is not treated, this “lazy eye” becomes progressively more disconnected from the brain and over time the problem becomes worse. This is called amblyopia. […] Concomitant squints are due to differences in the control of the extra ocular muscles. The severity of the squint can vary. […] Paralytic squints are rare. They are due to paralysis in one or more of the extra ocular muscles.

• #13 Squint – Zero To Finals

  https://zerotofinals.com/paediatrics/neurology/squint/

  Cases of squint in otherwise healthy children are usually idiopathic, meaning there is not a specific underlying cause. Other causes of squint include: Hydrocephalus, Cerebral palsy, Space occupying lesions, for example retinoblastoma, Trauma. […] Up until the age of 8 years the visual fields are still developing, therefore treatment needs to start before 8 years. The earlier the better. Delayed treatment increases the risk of the squint becoming permanent.

• #14 Strabismus: MedlinePlus Medical EncyclopediaLock

  https://medlineplus.gov/ency/article/001004.htm

  Strabismus is a disorder in which both eyes do not line up in the same direction. Therefore, they do not look at the same object at the same time. […] In someone with strabismus, these muscles do not work together. As a result, one eye looks at one object, while the other eye turns in a different direction and looks at another object. […] When this occurs, two different images are sent to the brain — one from each eye. This confuses the brain. In children, the brain may learn to ignore (suppress) the image from the weaker eye. […] If the strabismus is not treated, the eye that the brain ignores will never see well. This loss of vision is called amblyopia. Another name for amblyopia is „lazy eye.” […] Most of the time, the problem has to do with muscle control, and not with muscle strength.

• #14 Strabismus: MedlinePlus Medical EncyclopediaLock

  https://medlineplus.gov/ency/article/001004.htm

  A family history of strabismus is a risk factor. Farsightedness may be a contributing factor, often in children. Any other disease that causes vision loss may also cause strabismus. […] Eye muscle surgery may be needed if the eyes still do not move correctly. Different muscles in the eye will be made stronger or weaker. […] Eye muscle repair surgery does not fix the poor vision of a lazy eye. Muscle surgery will fail to improve vision if amblyopia has not been treated. […] Surgery is more often successful if done when the child is younger. […] If strabismus has occurred because of vision loss, the vision loss will need to be corrected before strabismus surgery can be successful. […] After surgery, the eyes may look straight, but vision problems can remain. […] Permanent vision loss in one eye may occur if treatment is delayed. If amblyopia is not treated by about age 11 years, it is likely to become permanent.

• #15 Adaptive mechanism of squint | PPT

  https://www.slideshare.net/slideshow/adaptive-mechanism-of-squint/60381846

  Adaptive mechanism of squint Diplopia Usually seen in acquired strabismus over 7-8 years of age In younger children, transient i.e. for 2-4 weeks Patient will fixate on an object with one fovea and see diplopic image from perifoveal retina of the deviated eye, with fovea of deviated eye suppressed […] Immature Visual System Occur when binocularity disrupted before 6 years of age Results in 1. Cortical suppression 2. Amblyopia 3. Monofixation syndrome 4. Anomalous Retinal Correspondence(ARC) […] Suppression Defined as temporary active cortical inhibition of image formed on retina of the deviated eye Occurs during binocular vision Disappears when deviating eye fixates […] Abnormal Retinal Correspondence Normal retinal correspondence(NRC) is binocular relationship in which true anatomic fovea of each eye are functionally linked together in occipital cortex ARC is when fovea of normal eye and extrafoveal point on retina of squinting eye acquire common representation ARC is adaptation to moderate angle infantile strabismus usually between 15-30 PD

• #16 Adaptive mechanism of squint | PPT

  https://www.slideshare.net/slideshow/adaptive-mechanism-of-squint/60381846

  Binocular sensory adaptation used to eliminate diplopia by accepting eccentric image location in deviated eye Allows brain to accept parafoveal images from deviated eye and superimposes with image from fixing eye New functional fovea called pseudofovea(PF) […] If strabismus of ARC patient corrected, image displaced from PF onto retina which is cortically noncorresponding, even if image falls on fovea, leading to diplopia called paradoxical diplopia If after neutralization of squint patient has diplopia, it means he has ARC paradoxical diplopia stays only for few weeks after surgery […] Large regional suppression Large angle strabismus or severe U/L image blur patients develop large suppression scotoma These patients will have no binocularity, peripheral fusion or ARC Can be intermittent […] Sensory Tests Diplopia tests Most dissociating 1. Maddox rod 2. Dark red filter 3. Worth 4 dot with room lights out Least dissociating 1. Bagolini striated lenses

• #17 Strabismus Causes and Treatment in Turkey – Bimaristan

  https://bi-maristan.com/en/eye-diseases/oculoplastics/strabismus/

  Strabismus, also known as squint, is a condition where the eyes fail to align properly, leading to asymmetry in eye movement. It affects 4% of people and can be permanent or temporary. […] Strabismus can cause the eyes to not work together, affecting one eye consistently or alternating between both. In congenital cases, the brain may ignore signals from the misaligned eye, leading to amblyopia. […] Strabismus is an optical defect that causes the eyes to move in a non-parallel and unbalanced manner so that the optical axes do not meet at a single point, causing diplopia and double vision for the patient. […] Strabismus or squint eyes have two basic types: Comitant strabismus and Incomitant strabismus. […] Incomitant strabismus occurs when the angle of deviation changes with the direction of gaze, often due to paralysis or weakness of the eye muscles.

• #18 Cyclic Esotropia

  https://www.eophtha.com/posts/cyclic-esotropia

  Cyclic esotropia is a rare form of non-accommodative convergent strabismus which present as 24-hour period of straight eye position followed by 24 hours of large-angle esotropia. […] The etiology of this rare form of convergent strabismus is unknown. Possible theories behind the evolution of such a strabismus include progressive loss of compensation of a latent strabismus, change of a central clock mechanism, and incomplete cerebral dominance, with interhemispheric conflict spontaneously or may be precipitated by a trigger. […] Some authors have also suggested the dysregulation of central nervous system pathways involved in the biological clock affecting oculomotor control such as those of the hypothalamus or superior colliculus. […] Nonsurgical approaches by botulinum toxin injections in customized dosages to one or both medial rectus muscles may be an alternative way to effectively treat this rare squint.

• #19 Pattern strabismus and torsion needs special surgical attention | Eye

  https://www.nature.com/articles/eye2014270

  Pattern strabismus is relatively common in strabismus practice. […] The exact mechanism of pattern strabismus is poorly understood even today. […] Various surgical options for pattern strabismus include procedures on superior/inferior oblique muscles if there is associated oblique dysfunction or transposition procedures on the rectus muscles in its absence. […] Etiology of pattern strabismus has evolved through many theories. Though there are various schools of thought, there is no unanimity regarding the exact pathophysiology of pattern strabismus. Proposed etiological mechanisms can be mechanical (peripheral) and neural (central). […] According to the theory of horizontal muscle overaction, an imbalance between the actions of the rectus muscles leads to pattern strabismus, for example the medial rectus muscles overact in downgaze and lateral rectus muscles overact in upgaze giving rise to a V esotropia.

• #20 Pattern strabismus and torsion needs special surgical attention | Eye

  https://www.nature.com/articles/eye2014270

  An imbalance of the cyclovertical muscles was also proposed to be one of the mechanisms for pattern strabismus. […] This theory is most popular and widely accepted and was put forward by Knapp in 1959. […] Anatomical factors like craniofacial anomalies, hydrocephalus, and heterotopy of muscle pulleys demonstrate pattern strabismus owing to abnormal vector force. […] The theory of sagittalisation of oblique muscles as a cause of pattern strabismus was put forward by Gobin. […] EOM pulleys are condensations of posterior tenons capsule composed of collagen, elastin, and smooth muscles, which act as the functional origin of EOMs. […] Several neural mechanisms have been proposed to explain pattern strabismus. […] Ocular torsion has been attributed as a major etiological factor for pattern strabismus by the author.

• #21 Pattern strabismus and torsion needs special surgical attention | Eye

  https://www.nature.com/articles/eye2014270

  Fundus torsion is also described as a marker for subsequent development of inferior oblique overaction in cases of infantile esotropia by Eustis and Nussdorf. […] Good correlations were found between fundus intorsion, superior oblique muscle overaction, and A patterns; and between fundus extorsion, inferior oblique muscle overaction, and V patterns in a study conducted by Deng et al. […] An experimental study published by Kushner evaluated whether ocular torsion is a primary factor for the development of pattern strabismus, or is just a contributing factor. […] It has been argued that ocular torsion may lead to heterotopy of orbital pulleys and displacement of pulleys may result in altered vector forces in the presence of cyclotorsion.

• #22 Strabismus | Causes, Symptoms & Surgery | Britannica

  https://www.britannica.com/science/strabismus

  strabismus, misalignment of the eyes. The deviant eye may be directed inward toward the other eye (cross-eye, or esotropia), outward, away from the other eye (exotropia), upward (hypertropia), or downward (hypotropia). The deviation is called concomitant if it remains constant in all directions of gaze and incomitant if the degree of misalignment varies with the direction of gaze. […] Congenital, or infantile, strabismus appears in infancy and is presumably due to defects present at birth that are poorly understood. However, given the strong tendency for strabismus to run in families, the causes undoubtedly have some genetic component. […] Acquired strabismus appears later in life and has many potential etiologies. For example, acquired strabismus can be due to diseases or trauma affecting the actual muscles responsible for moving the eye or the nerves or brain stem centres controlling those muscles.

• #23 Strabismus | Causes, Symptoms & Surgery | Britannica

  https://www.britannica.com/science/strabismus

  In addition, poor vision in one or both eyes can lead to sensory strabismus, in which the eye with the poorest vision drifts slightly over time. […] In children, a common contributor to acquired strabismus is farsightedness (hyperopia), which, when severe enough, can secondarily cause the eyes to cross as the child tries to focus on an object (accommodative esotropia).

• #24 Azthena logo with the word Azthena

  https://www.news-medical.net/health/What-is-Strabismus.aspx

  More than half of all children with a squint have congenital strabismus, mostly due to a lack of nerve control over the movement of otherwise healthy eye muscles. […] Adults develop strabismus less commonly, and it may be the result of botulism, which paralyzes some muscles, diabetes, Graves disease or Guillain-Barre syndrome, injury to the eye, or the brain, among other causes. […] Diagnosis is by means of standard eye tests, including covering and uncovering the eye to watch the shift in the pupillary direction, light reflex tests and retinal testing, as well as visual acuity. […] Finally, eye surgery is often required to strengthen or weaken various eye muscles, so that both eyes move together in the same direction. […] Uncorrected squints in children may result in vision loss. Strabismus may even recur, following treatment, and so careful monitoring is mandatory.

• #24 Azthena logo with the word Azthena

  https://www.news-medical.net/health/What-is-Strabismus.aspx

  Strabismus, squint, or crossed eyes, is a condition in which both eyes do not look in the same direction at the same time. It occurs because the eyes do not move in synchrony with each other, resulting in different positions of the two eyes when looking at an object. […] One or more of the six muscle pairs that control eye movement are out of harmony. […] In strabismus, each eye sends a different image to the brain, which is confusing. When this starts in childhood, before the eye-brain connections are firmly in place, this eventually results in the brain ignoring one of the images. […] What this really means is that the brain always suppresses the image from one eye, resulting in the lack of processing and feedback to the nerve cells of that eye. This finally causes an otherwise functionally and physically normal eye to stop seeing. This condition is called amblyopia.

• #25 Squint Eye: Meaning, Causes, Treatment & Surgery

  https://dpuhospital.com/blog/squint-eye-meaning-causes-treatment-surgery/

  Strabismus, also known as crossed eyes or squint eyes, is a vision disorder that affects a person’s ability to align both eyes simultaneously. […] Strabismus can occur in one or both eyes and be constant or intermittent. […] If left untreated, strabismus can lead to amblyopia, also known as lazy eye, which can cause permanent vision loss in the affected eye. […] Determining the underlying cause of strabismus can help treat and manage the condition properly. […] Problems with the muscles that control eye movement: Strabismus can occur when the muscles that control eye movement are not working well. […] Nerve abnormalities that affect eye movement: Strabismus can also occur due to abnormalities in the nerves that control eye movement. […] Brain injuries or neurological conditions: Traumatic brain injuries, strokes, and other neurological problems can affect the muscles or nerves that control eye movement and lead to strabismus.

• #25 Squint Eye: Meaning, Causes, Treatment & Surgery

  https://dpuhospital.com/blog/squint-eye-meaning-causes-treatment-surgery/

  Prolonged or untreated amblyopia: Amblyopia, also known as „lazy eye,” is a condition where one eye has reduced visual acuity. If left untreated, amblyopia can lead to strabismus as the brain tries to compensate for the weaker eye. […] The treatment of strabismus, also known as squint eyes, can vary depending on the type and severity of the condition. […] The treatment approach will depend on the type and severity of strabismus, as well as the age and overall health of the patient. […] If left untreated, a squint (strabismus) can cause several problems, including amblyopia (lazy eye). […] It is vital to seek treatment for a squint as early as possible to prevent these complications from occurring.

• #26 Squinting of Eyes Unlocking Clarity Understanding & Finding Relief

  https://vijayanethralaya.com/squinting-of-eyes-causes-effects-and-remedies/uncategorized-en/

  Squinting of eyes is a common phenomenon that many of us experience in our daily lives. […] Squinting can be both a reflexive action and a sign of underlying issues. […] Persistent or frequent squinting can indicate an underlying problem. […] Refractive errors, such as nearsightedness (myopia), farsightedness (hyperopia), and astigmatism, can lead to squinting. […] Lazy eye, a condition where one eye is weaker than the other, can result in squinting as the brain tries to favor the stronger eye. […] Strabismus, or crossed eyes, is a condition where the eye muscles do not work together properly. […] Frequent squinting can lead to eye strain, which can cause headaches and discomfort. […] Persistent squinting, if left unaddressed, can lead to reduced vision, especially in children.

• #27 Strabismus | Calgary Guide

  https://calgaryguide.ucalgary.ca/strabismus-pathogenesis-and-clinical-findings/strabismus/

  Strabismus: Pathogenesis and clinical findings Microvascular dysfunction, trauma, or compression of oculomotor nerve […] Thyroid eye disease (see Thyroid Eye Disease slide for pathogenesis) […] Inflammatory processes Thickening fibrosis of extraocular muscles, most commonly the inferior rectus muscle (functions to rotate the eye and depress the gaze) […] Dysfunction of the abducens nerve (CN VI: innervates the ipsilateral lateral rectus muscle which abducts the eye [turns it laterally]) […] Unclear process […] Binocular diplopia: double vision when both eyes are open, and absent when either eye is closed […] Psychosocial consequences: negative impact to mental health due to social bias or abuse, social anxiety, and difficulties with self-image.

• #28 Convergent squint in myopia by Dr… – Sandhurst Eye CentreFacebookShared with Public

  https://www.facebook.com/sandhursteyecentre/posts/convergent-squint-in-myopia-by-dr-pierre-vercueilany-misalignment-of-the-eyes-is/923478567822229/

  Convergent strabismus associated with high myopia (short sightedness) is a rare abnormality of ocular motility characterized by the presence of esotropia and hypotropia (lowering), with restricted abduction and elevation. […] With the evolving understanding of the pathogenesis, consensus has now been reached that strabismus with high myopia is usually the consequence of the supertemporal protrusion of the elongated eye globe through the muscle cone, leading to an inferior displacement of the lateral rectus muscle and nasal displacement of the superior rectus muscle. […] The connective tissue band between the lateral rectus muscle and the superior rectus muscle degenerates as the globe protrudes out of the muscle cone. The superior rectus then becomes and adductor, pulling the eye inwards and the lateral rectus becomes an infraductor pulling the eye downwards.

• #29 Squint – National Institute of Ophthalmology

  https://www.nioeyes.com/squint/

  Sometimes a squint is seen right since birth or within first six months from birth, where in both eyes are turned inwards towards the nose. […] The other frequent cause of squint is having high plus power glasses. Such children have glasses of + 4-5D or even higher. […] The presence of any other eye problem which hampers vision can also give rise to squint, where in the eye deviates more commonly outwards towards the ear. […] Some other causes are- spectrum of syndromes such as Duanes retraction syndrome, Mobius syndrome, Brown syndrome which have squint as the main feature. […] Over action or under action or restriction of muscles can also cause eyes to squint. […] There are three types of squint- convergent squint, essential infantile esotropia, and divergent squint. […] The presence of some other eye problems which hampers vision can give rise to a squint, wherein the eye deviates outwards towards the ear. This type of squint is known as divergent squint. It can also develop if the patient has lost his/ her eye sight of one eye due to an injury, accident, or other causes.

• #30 Strabismus Causes and Treatment in Turkey – Bimaristan

  https://bi-maristan.com/en/eye-diseases/oculoplastics/strabismus/

  The causes vary from case to case, and in some cases, the cause remains unknown; here are the most important causes: Poor vision in one eye, inflammatory conditions such as meningitis and polyneuritis, cerebral vascular lesions such as cerebral aneurysms, Down syndrome, hydrocephalus, brain tumors, stroke, and injury to the nerves responsible for moving the eye muscles. […] Squinting has many different symptoms, including visual stress, difficulty reading, and double vision. […] It results in many visual, cosmetic, and sometimes psychological complications: It can lead to a vision disorder such as glaucoma. One of the main complications is the development of amblyopia, or lazy eye, which results from the brain neglecting images coming from one eye. […] Treatment varies depending on the causative factor. If hyperopia is the cause, glasses or contact lenses can be used to correct it. Amblyopia, which can be both a cause and a consequence of squinting, can be treated by covering the healthy eye with a patch to stimulate the affected eye. In some cases, surgery may be needed to correct the muscles of the affected eye to restore the eyes balance.

• #31 Diplopia (Double Vision): Background, Pathophysiology, Epidemiology

  https://emedicine.medscape.com/article/1199512-overview

  Binocular diplopia (or true diplopia) is a breakdown in the fusional capacity of the binocular system. The normal neuromuscular coordination cannot maintain correspondence of the visual objects on the foveae of the two eyes. Rarely, fusion cannot occur because of dissimilar image size, which can occur after changes in the optical function of the eye after refractive surgery (eg, LASIK) or after a cataract is replaced by an intraocular lens or because of aniseikonia, which represents a discrepancy in image size perceived by the two eyes. […] Monocular diplopia may result from abnormal light transmission to the retina (eg, corneal distortion or scarring, multiple openings in the iris, cataract or subluxation of the natural lens or pseudophakic lens implant, vitreous abnormalities, retinal conditions). Monocular diplopia must be distinguished from metamorphopsia, in which objects appear misshapen.

• #32 Strabismus | Squint – Types, Causes, Symptoms, Diagnosis, Treatment & Prevention

  https://www.medindia.net/health/conditions/strabismus.htm

  Paralytic squint due to a weakness in the muscles moving the eyes or the nerves supplying them eg. myasthenia gravis, nerve paralysis. […] Restrictive squint due to a physical restriction on the movement of the muscles eg. thyroid eye disease, tumors in the orbit. […] Suppression of image in the deviating eye to prevent double vision. Thus the higher degrees of binocular vision are affected. […] A poor adaptation made by the sensory mechanisms to maintain some sort of binocular vision even in the presence of a squint. This should be specifically looked for in every patient of squint prior to surgical correction. If present, this should be addressed, otherwise surgical correction of the squint can lead to double vision.

• #33

  https://lupinepublishers.com/ophthalmology-journal/fulltext/neural-mechanisms-and-causes-of-Non-Traumatic-and-Non-Pathological-strabismus.ID.000162.php

  The presence of suppression in strabismus when the two eyes are open appears to relate to altered cortical binocular integration and interocular inhibitory interactions in V1. […] The aforementioned areas in the brain are possibly affected simultaneously, depending on the severity of an individuals condition and the age of onset of the symptoms. […] The various possible causes of such an abnormal function between the eyes and the brain, are extensively discussed on the Origins of strabismus review, written by Quoc and Milleret in 2014. […] This review describes in detail a considerable number of possible errors and abnormalities in the visual pathway which pave the way to scientists for additional research towards the understanding of the binocular disruption. […] However, it remains unknown what happens first; the loss of binocular fusion or the eye misalignment? This is a question that, if answered, will certainly shed light on the main causes of strabismus which will probably make strabismus treatment more specific and hopefully more efficient for both adults and children.

• #34

  https://link.springer.com/article/10.1007/s00417-022-05935-9

  All these unequivocally point to cerebral involvement in eye misalignment pathogenesis. […] The ocular deviation is not a disease in itself but a consequence of an underlying problem ranging from systemic, ocular, and neurological diseases to genetic syndromes and to acquired injury to the structures involved in vision. […] Optimal medical treatment should be directed to the source. […] However, in most strabismus cases, there is little or no evidence of abnormalities in the EOMs. […] In addition, the presence of co-existing CNS abnormalities suggests that the CNS plays a role in strabismus pathogenesis. […] Considering that multiple causes, along the periphery-center axis, can be behind the ocular deviation, different treatment strategies tailored to the precise strabismus causes might be needed.

• #35

  https://lupinepublishers.com/ophthalmology-journal/fulltext/neural-mechanisms-and-causes-of-Non-Traumatic-and-Non-Pathological-strabismus.ID.000162.php

  The combination of these exercises features VT as a promising holistic treatment approach of strabismus. […] Vision therapy procedures applied in different strabismic cases indicate that a part or even full binocular fusion and stereopsis may be recovered along with the orthoptic alignment of the eyes. […] A variety of combination of VT activities is recommended by different authors depending on the age of onset, the diagnostic factors, the cognitive capacity of the patient and the cooperation with the therapist. […] As far as the differences in VT procedures in children from 6 ~ 7 years of age and adults is concerned, a similar approach is observed by the different authors, yet with minor variations not only in the order of activities, but also in incorporating other exercises. […] Hopefully, more research in the neural mechanisms and causes of strabismus, vision therapy procedures and studies investigating the changes in the affected brain areas before and after vision therapy, shall occur in the future.

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