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Squint

A squint, medically termed strabismus, is a visual disorder in which the eyes fail to align properly, with one eye deviating inward, outward, upward, or downward relative to the other when focusing on an object.^[1] This misalignment disrupts binocular vision and can lead to symptoms such as double vision (diplopia), reduced depth perception, and eye strain.^[2] Strabismus affects approximately 2% to 4% of the global population, with a higher prevalence in children—estimated at 4% in the United States—though it can manifest at any age due to congenital factors or later-onset causes.^[3]^[4] The condition arises from various etiologies, including imbalances in the extraocular muscles controlling eye movement, uncorrected refractive errors like hyperopia (farsightedness), neurological issues such as cranial nerve palsies, genetic predispositions, or trauma to the orbit or brain.^[5]^[6] Common types include esotropia (inward deviation, or "crossed eyes"), exotropia (outward deviation), and vertical deviations like hypertropia.^[7] In infants and young children, it often appears as an infantile form linked to immature visual development, while adults may develop it secondary to conditions like thyroid eye disease, stroke, or myasthenia gravis.^[8]^[9] Untreated strabismus can result in amblyopia (lazy eye), where the brain suppresses input from the deviating eye to avoid confusion, potentially leading to permanent vision loss in that eye if not addressed early.^[10] Diagnosis typically involves a comprehensive eye examination, including cover testing to assess alignment and refraction to identify underlying errors.^[5] Treatment is multifaceted and aims to restore alignment and binocular function: non-surgical options include corrective lenses for refractive errors, eye patching or atropine drops to treat amblyopia, and prism lenses to alleviate double vision; surgical intervention, involving adjustment of eye muscles, is common for persistent cases and boasts success rates of 70-90% in improving alignment.^[2]^[7] Early intervention, ideally before age 7, is crucial for optimal visual outcomes, though adults can also benefit from therapy to enhance quality of life and cosmetic appearance.^[6]

Definition and Classification

Definition

Squint, also known as strabismus, is a visual disorder characterized by the misalignment of the eyes, where the visual axes do not point in the same direction when focusing on an object, resulting in one eye deviating inward, outward, upward, or downward.^[2]^[1] This condition disrupts the normal coordination between the eyes, preventing them from working together effectively.^[5] Normal binocular vision requires the visual axes of both eyes to intersect at the fixation point to fuse images into a single, three-dimensional perception with depth.^[11] In squint, this alignment is compromised, leading to diplopia (double vision) or suppression of input from the deviating eye as the brain adapts to avoid confusion.^[12] The misalignment can affect one or both eyes and may manifest as various types based on the direction of deviation. Key terminology includes esotropia for inward deviation toward the nose, exotropia for outward deviation, hypertropia for upward deviation, and hypotropia for downward deviation.^[6] Squint can be constant, occurring all the time, or intermittent, appearing only under certain conditions such as fatigue or distance viewing.^[2]^[7] Squint affects approximately 2% to 4% of the population, with higher prevalence in children where it often presents before school age.^[13]^[5]

Types

Strabismus, commonly known as squint, is classified in multiple ways to reflect its clinical variations, primarily by the direction of eye deviation, age of onset, and underlying mechanisms of misalignment. These classifications help clinicians differentiate between forms that may require distinct approaches to evaluation and management.^[5]^[14] The most fundamental classification is by direction of deviation. Esotropia, or convergent squint, involves inward deviation of one or both eyes toward the nose, often noticeable when focusing on near objects. Exotropia, or divergent squint, features outward deviation away from the nose, which may be constant or intermittent. Vertical deviations include hypertropia, where one eye drifts upward relative to the other, and hypotropia, where it drifts downward; these can occur in isolation or combined with horizontal deviations. Torsional deviations, such as incyclotorsion (inward twisting) or excyclotorsion (outward twisting), are less common but contribute to complex misalignments.^[5]^[14] Classification by onset distinguishes congenital or infantile strabismus, which manifests at birth or within the first six months of life, from acquired strabismus that develops later, typically after six months. Infantile esotropia serves as a classic example of the congenital type, presenting as a constant inward deviation in otherwise healthy infants and affecting approximately 1 in 100 to 500 individuals. In contrast, acquired forms may emerge in childhood or adulthood due to evolving factors, though specific etiologies are varied.^[5]^[14] Additional classifications address functional aspects and patterns. Accommodative squint refers to esotropia triggered by refractive errors like hyperopia, where excessive focusing effort leads to over-convergence. Paralytic squint arises from dysfunction in ocular motor nerves or muscles, resulting in variable misalignment. Restrictive squint stems from mechanical restrictions preventing full eye movement, such as orbital scarring. Strabismus is further categorized as comitant, where the deviation angle remains consistent across all gaze directions, or incomitant, where it varies by gaze position, often indicating underlying nerve or muscle issues. Subtypes include alternating squint, in which either eye can fixate while the other deviates interchangeably, and monocular squint, where one eye consistently deviates. Intermittent exotropia exemplifies an acquired, often comitant form common in children, characterized by periodic outward drift, particularly during fatigue or distant viewing. Pattern deviations, such as A- or V-patterns, describe horizontal misalignments that intensify in specific vertical gazes, adding nuance to directional classification.^[5]^[14]^[15]

Causes and Pathophysiology

Causes

Squint, or strabismus, arises from a variety of etiological factors that disrupt normal eye alignment. Genetic influences play a significant role, with family history substantially increasing the risk of developing the condition. Studies have shown a higher prevalence of strabismus among relatives of affected individuals, indicating a hereditary component.^[16] Specific genetic mutations, such as those in the PAX6 gene, are implicated in certain congenital forms, where missense mutations can lead to familial concomitant strabismus.^[17] Developmental causes often stem from issues in early visual maturation. Poor development of binocular fusion during infancy contributes to infantile esotropia, a common type of inward deviation.^[18] Uncorrected refractive errors, particularly hyperopia (farsightedness), can trigger accommodative esotropia by overstimulating eye convergence to focus on near objects.^[19] Neurological factors account for many acquired cases. Palsies of the cranial nerves controlling eye movements—specifically the third (oculomotor), fourth (trochlear), or sixth (abducens) nerves—impair muscle function and cause misalignment.^[3] Brain injuries, such as those from trauma or stroke, and intracranial tumors can also disrupt neural pathways, leading to strabismus.^[20] Other causes include mechanical and systemic conditions. Orbital fractures may restrict eye movement, mimicking nerve palsies and resulting in deviation.^[21] Thyroid eye disease causes restrictive strabismus through extraocular muscle enlargement and inflammation.^[22] Myasthenia gravis, an autoimmune disorder affecting neuromuscular transmission, can produce variable misalignment.^[21] Congenital anomalies like Duane syndrome involve aberrant innervation of eye muscles, leading to limited abduction and retraction on adduction.^[23] Certain risk factors heighten susceptibility to specific causes. Prematurity and low birth weight are strongly associated with infantile esotropia, likely due to immature visual system development.^[18] In children, uncorrected farsightedness increases the likelihood of accommodative esotropia if refractive errors go unaddressed.^[19]

Pathophysiology

Strabismus, or squint, arises from an imbalance in the coordinated action of the extraocular muscles, which are responsible for precise eye alignment and movement. Each eye is controlled by six extraocular muscles: the superior and inferior recti, medial and lateral recti, and superior and inferior obliques. These muscles are innervated by the oculomotor (cranial nerve III), trochlear (cranial nerve IV), and abducens (cranial nerve VI) nerves, originating from brainstem nuclei. Imbalance in muscle tone or innervation leads to ocular deviation, disrupting normal conjugate gaze.^[5] Neural control of eye movements involves the brainstem's oculomotor nuclei and supranuclear pathways, which coordinate conjugate eye movements through interconnected circuits in the midbrain, pons, and cerebellum. Disruptions in these pathways, such as hypoplasia of the oculomotor nuclei or abnormal signaling in the pontine reticular formation, can impair conjugate gaze and contribute to strabismic misalignment. In infantile or congenital cases, early developmental anomalies in these neural structures prevent the establishment of proper binocular coordination.^[24]^[5] Fundamental to this control are Hering's law of equal innervation, which dictates that yoke muscles in both eyes receive equal neural input for conjugate movements, and Sherrington's law of reciprocal inhibition, which ensures that agonist muscle activation is matched by antagonist relaxation. In congenital strabismus, breakdown of these laws during infancy—due to genetic or environmental factors affecting neural maturation—results in persistent deviation, as the developing visual system fails to calibrate equal innervation across eyes. For instance, unequal innervation to yoke muscles can exacerbate esotropia or exotropia in primary gaze positions.^[25]^[5] This misalignment disrupts binocular vision by projecting non-corresponding images onto the retinas, preventing fusion and the development of stereopsis. The brain responds by suppressing input from the deviating eye to avoid diplopia, which can lead to amblyopia if prolonged during critical visual development periods. Suppression occurs at cortical levels, particularly in the visual cortex, where interocular rivalry favors the dominant eye's input.^[26] In restrictive forms of strabismus, mechanical factors such as orbital restrictions or muscle fibrosis limit passive eye movement. Conditions like congenital fibrosis of the extraocular muscles involve fibrotic replacement of muscle fibers, often due to aberrant innervation from cranial nerve misrouting or primary myopathy, leading to fixed deviations and reduced motility. These restrictions differ from paretic types by involving physical tethering rather than neural deficits alone.^[27]

Signs and Symptoms

Ocular Signs

Squint, or strabismus, manifests through noticeable ocular misalignment where the eyes fail to point in the same direction simultaneously. This can present as esotropia, with one eye turning inward toward the nose; exotropia, where the eye drifts outward; or vertical deviations such as hypertropia (upward) or hypotropia (downward).^[1]^[6] Additional common symptoms include headaches, eye strain, closing or covering one eye in bright light or during near tasks, and frequent blinking or squinting.^[2]^[7] To compensate for the misalignment and minimize visual discomfort, individuals may adopt abnormal head postures, including a head tilt or face turn—for instance, turning the head away from the affected side in cases of sixth nerve palsy to align the eyes better.^[28] Strabismus frequently coexists with refractive errors such as hyperopia, myopia, or astigmatism. Visual symptoms primarily involve disruptions in binocular vision. Adults often experience diplopia, or double vision, due to the brain receiving conflicting images from the misaligned eyes.^[5] In children, however, the developing visual system typically suppresses the image from the deviating eye to avoid diplopia, which can lead to reduced visual acuity in that eye if prolonged.^[1]^[6] Untreated strabismus often begins intermittently, triggered by factors like fatigue or distance viewing, but can progress to a constant deviation over time, particularly in childhood-onset cases.^[5]^[1]

Associated Effects

One of the primary associated effects of squint, or strabismus, is amblyopia, commonly known as lazy eye, which involves reduced visual acuity in the deviating eye resulting from active cortical suppression by the brain to avoid double vision. This suppression disrupts normal visual development, leading the brain to favor input from the non-deviating eye. In untreated cases, amblyopia develops in approximately 40-50% of children with strabismus, highlighting its high prevalence as a secondary complication.^[29]^[30] Strabismus also frequently results in the loss of stereopsis, or binocular depth perception, due to the disruption of normal binocular fusion where corresponding retinal images fail to align properly. Without this fusion, individuals rely on monocular cues for depth judgment, which are less precise and can impair tasks requiring accurate spatial awareness, such as driving or sports. This effect is particularly pronounced in early-onset strabismus, as the critical developmental window for stereopsis (typically 3-6 months to 8 years) is compromised, often leading to permanent deficits if not addressed.^[31] As a sensory adaptation to chronic misalignment, the brain may develop anomalous retinal correspondence (ARC), remapping visual inputs so that non-corresponding retinal points are perceived as aligned, thereby minimizing diplopia and promoting a single visual field. This neural plasticity, most common in small-angle strabismus (less than 5 degrees deviation), occurs primarily in childhood through cortical reorganization in the visual cortex, suppressing eccentric retinal areas to achieve pseudo-binocular vision. However, ARC can complicate treatment by maintaining the deviation even after alignment correction.^[32] Untreated strabismus during the critical period of visual development (from birth to approximately 7-8 years) carries the risk of permanent visual loss, including irreversible amblyopia and diminished stereopsis, as the visual system loses plasticity beyond this window. In children, these visual impairments can extend to psychosocial consequences, such as lowered self-esteem, experiences of bullying, and social isolation due to perceived differences in appearance. Studies indicate higher rates of mental health issues, with children showing 1.6 times greater odds of depression and adults exhibiting prevalence rates up to 33% for depression compared to 14% in non-strabismic individuals. Additionally, adults may face anxiety, avoidance of eye contact, and employment challenges stemming from negative social biases.^[5]^[33]^[34]

Diagnosis

Clinical Evaluation

The clinical evaluation of squint, or strabismus, begins with a detailed patient history to identify potential etiologies and guide further assessment. Key elements include the age of onset, which helps differentiate congenital from acquired forms; family history of strabismus or related ocular conditions; birth complications such as prematurity or low birth weight; progression of refractive errors like hypermetropia; presence of diplopia, which is more common in older children with acute deviations; and abnormal head postures that may compensate for misalignment.^[35]^[36]^[37] Visual acuity testing follows to detect amblyopia or refractive contributions to the squint. In adults and cooperative children, standardized methods like the Snellen chart are used, while age-appropriate tools such as picture charts, Lea symbols, or preferential looking tests (e.g., Teller acuity cards) are employed for younger patients to measure monocular and binocular acuity with optimal refractive correction.^[35]^[36] Ocular motility is assessed through ductions, which evaluate monocular eye movements in cardinal directions, and versions, which test binocular pursuits to identify restrictions, overactions, or incomitancy. The cover test, performed at distance and near fixations, is essential: the cover-uncover test detects phorias by observing refixation upon uncovering, while the alternate cover test dissociates the eyes to reveal tropias through movement of the uncovered eye.^[35]^[38]^[36] Alignment is quantified using the Hirschberg test for gross estimation, where the position of a corneal light reflex is observed; asymmetry indicates deviation, with approximately 15 to 21 prism diopters per millimeter of displacement from the pupil center, depending on corneal radius. For precise measurement, the prism cover test neutralizes the deviation with prisms to determine the exact angle in prism diopters.^[35]^[38]^[37] Binocular function is evaluated to assess sensory adaptations like suppression or fusion. The Worth 4-dot test detects suppression by presenting polarized lights, where failure to report all dots from one eye indicates suppression. Stereopsis is measured using tests such as the Titmus fly, which quantifies depth perception through random dot patterns, with normal stereoacuity at 40 seconds of arc or better (≤40 seconds of arc) in non-strabismic individuals.^[35]^[36]^[38]

Diagnostic Tests

Refraction testing, including cycloplegic refraction, is essential to identify uncorrected refractive errors that may contribute to or exacerbate strabismus, particularly hyperopia leading to accommodative esotropia. Cycloplegic agents, such as cyclopentolate, temporarily paralyze accommodation to allow accurate measurement via retinoscopy or autorefraction, ensuring a precise prescription that can influence eye alignment.^[39] This exam is routinely performed in pediatric cases to rule out refractive causes before considering other etiologies.^[40] Fundoscopy and slit-lamp examination are conducted to detect underlying ocular abnormalities, such as retinal detachments, tumors, or anterior segment issues like cataracts, which could underlie or mimic strabismus symptoms.^[41] The slit-lamp provides detailed visualization of the cornea, iris, and lens, while dilated fundoscopy assesses the posterior segment for pathologies like optic nerve anomalies or macular issues that might affect alignment.^[42] These tests help exclude organic causes in the diagnostic workup.^[43] Imaging modalities, including magnetic resonance imaging (MRI) and computed tomography (CT), are indicated when neurological or structural causes are suspected, such as cranial nerve palsies from tumors or strokes.^[44] High-resolution MRI can visualize extraocular muscle atrophy, nerve involvement, or orbital masses, aiding in confirming paralytic strabismus.^[45] Orbital ultrasound serves as a non-invasive initial tool to evaluate for masses, inflammation, or post-traumatic changes contributing to restrictive strabismus.^[46] Electrophysiological tests, such as electromyography (EMG), assess extraocular muscle function in cases of suspected paralytic strabismus, detecting abnormalities in nerve conduction or muscle activity due to conditions like myasthenia gravis.^[47] Visual evoked potentials (VEP) provide an objective measure of visual pathway integrity, particularly useful in evaluating associated amblyopia by identifying delays in cortical response from the amblyopic eye.^[48] For differential diagnosis, thyroid function tests, including TSH and free T4 levels, are recommended in adults with new-onset strabismus to screen for thyroid eye disease, which can cause restrictive patterns.^[49] Genetic screening may be pursued in congenital cases with family history or syndromic features, targeting genes like those involved in congenital fibrosis syndromes via whole exome sequencing.^[50] Emerging diagnostic tools as of 2025 include artificial intelligence (AI)-based systems for automated strabismus detection and classification. Deep learning models analyze facial images or cover test videos to quantify deviations, offering potential for improved screening in resource-limited settings, though they are not yet standard in clinical practice.^[51]

Management

Non-Surgical Options

Non-surgical options for managing strabismus primarily focus on correcting underlying refractive errors, treating associated amblyopia, and improving eye alignment through therapeutic interventions, particularly in children where neuroplasticity allows for better outcomes. These approaches aim to enhance binocular vision and prevent long-term visual deficits without invasive procedures. Spectacle correction is a cornerstone treatment, especially for accommodative esotropia, where hyperopia triggers excessive convergence. A full cycloplegic refraction is performed to determine the precise prescription, often involving plus lenses to relax accommodation and reduce the inward deviation; this can fully correct the misalignment in fully accommodative cases, with studies showing improved stereoacuity post-correction.^[52]^[53] Patching and occlusion therapy address amblyopia, a common associated effect of strabismus where the weaker eye is suppressed. The stronger eye is covered for 2-6 hours daily, or alternating with atropine penalization drops to blur its vision, forcing use of the deviated eye; meta-analyses indicate significant reduction in deviation angles and improved visual acuity in pediatric cases when initiated before age 7.^[54]^[53] Vision therapy, including orthoptic exercises, promotes fusion and stereopsis through targeted activities like pencil push-ups or computer-based training to strengthen eye coordination. Prism glasses may be incorporated temporarily to shift images and alleviate diplopia, achieving alignment in 80% of small-angle cases over time; virtual reality-enhanced programs have shown higher rates of orthophoria in follow-up trials, including post-surgical cases.^[53] Botulinum toxin injections weaken overactive extraocular muscles, offering a reversible alternative for select cases like acute esotropia or residual deviations; success rates reach 70% in maintaining alignment for up to 36 months, particularly in children avoiding general anesthesia.^[55]^[53] Regular monitoring through follow-up examinations is essential, especially for intermittent strabismus in children under 8 years, to track progression, adjust therapies, and intervene early if alignment worsens; pediatric ophthalmologists recommend visits every 3-6 months to optimize outcomes.^[54]

Surgical Options

Surgical intervention for strabismus is indicated when non-surgical treatments fail to correct persistent ocular deviation, particularly in cases involving large angles of misalignment such as esotropia greater than 15 prism diopters or exotropia greater than 20 prism diopters, as well as in restrictive or paralytic forms where muscle imbalance cannot be adequately managed conservatively.^[5] These indications aim to improve eye alignment, enhance binocular vision, and mitigate psychosocial effects from disfigurement.^[56] Timing of surgery is ideally sequenced after addressing any associated amblyopia to maximize visual outcomes, though early alignment can sometimes aid amblyopia resolution in select cases.^[5] For congenital strabismus, procedures are often performed between 6 months and 2 years of age to support critical periods of visual development and stereoacuity.^[5] The primary surgical technique is recession-resection, which weakens an overactive extraocular muscle by recessing its insertion posteriorly (typically 4-6 mm for horizontal recti) while strengthening the antagonist muscle through resection (shortening by 3-5 mm excision).^[56] Adjustable sutures are frequently incorporated to allow intraoperative or immediate postoperative adjustment of muscle tension, enabling fine-tuning of alignment within 5-7 days under local anesthesia.^[56] Horizontal strabismus, such as esotropia or exotropia, is addressed by targeting the medial or lateral rectus muscles, whereas vertical deviations like hypertropia involve the superior or inferior rectus and oblique muscles, often using recession of the inferior oblique or tucking of the superior oblique.^[57] Surgical approaches may be unilateral for smaller deviations or bilateral for larger angles exceeding 50 prism diopters, with bilateral methods providing more symmetric correction and reducing the risk of induced deviations in the fellow eye.^[5] Complications of strabismus surgery, though rare overall, include over- or under-correction leading to residual misalignment, postoperative infection with an incidence of approximately 0.14%, and anesthesia-related risks such as the oculocardiac reflex occurring in 14-90% of cases, which is managed with anticholinergic agents.^[58] Reoperation rates are approximately 20%, primarily due to recurrent deviation or unsatisfactory alignment, particularly in esotropic cases.^[58]^[59]

Prognosis and Epidemiology

Prognosis

The prognosis for strabismus, also known as squint, varies based on the age of onset, timeliness of intervention, and adherence to treatment, with overall success rates for achieving good ocular alignment ranging from 60% to 80% following surgical correction.^[60] Recovery from associated amblyopia is most effective when initiated before age 7, as visual plasticity diminishes significantly thereafter, leading to suboptimal improvements in visual acuity and binocular function.^[61] Early intervention, particularly in childhood, substantially enhances the likelihood of restoring binocular vision and fusion, whereas adult-onset strabismus often yields poorer recovery of these functions due to longstanding suppression and neural adaptations.^[62]^[63] If left untreated, strabismus can result in permanent amblyopia, irreversible loss of depth perception (stereopsis), and psychosocial challenges such as reduced self-esteem and social anxiety that persist into adulthood.^[30]^[64] Recurrence of misalignment occurs in up to 25% of cases post-treatment, often necessitating additional surgery, and patients require lifelong monitoring to detect changes influenced by age, neurological factors, or refractive shifts.^[65]^[66] Recent studies indicate improved outcomes with non-surgical approaches, such as prismatic correction achieving resolution rates up to 81% in select pediatric cases of strabismus-related diplopia; however, significant gaps remain in psychosocial support for adults, where emotional and quality-of-life burdens are often inadequately addressed.^[67]^[68]

Epidemiology

Strabismus affects approximately 2% to 5% of the global population, with a pooled prevalence of 1.93% based on a systematic review and meta-analysis of 56 studies encompassing over 600,000 participants across various regions.^[69] In the United States, prevalence is similarly estimated at 2% to 5% overall, but it is higher among children, reaching up to 4% in those under 6 years old according to population-based surveys.^[5]^[70] Esotropia tends to be more prevalent in European populations, where studies report esotropia rates around 0.8% compared to 0.3% for exotropia, resulting in an esotropia-to-exotropia ratio of 2:1.^[71] In contrast, exotropia predominates in Asian regions, with prevalence ratios as high as 9:1 favoring exotropia over esotropia in school-aged children.^[72] Demographic patterns show no significant overall gender difference in strabismus prevalence, with rates nearly identical at about 2.58% for both males and females in horizontal strabismus cases from a meta-analysis of 42 population-based studies.^[73] However, certain subtypes exhibit variations; for instance, intermittent exotropia is nearly twice as common in females.^[74] Risk is substantially elevated in premature infants, with incidence rates reaching 15% to 20% in low birth weight cohorts and up to 42% in very preterm individuals with gestational ages below 32 weeks, far exceeding the 2% to 4% seen in full-term children.^[75]^[76] Geographic variations highlight higher reported rates in developing countries, such as 17.9% in Ethiopian populations, potentially linked to delayed screening and limited access to early detection.^[77] Ethnic differences also influence subtype distribution, with exotropia being more common than esotropia in African populations, including African American children where exotropia accounts for a greater proportion of cases compared to white children.^[78] Overall trends in strabismus prevalence remain stable at 2% to 5% globally, though improved pediatric screening programs have led to increased detection rates in children, particularly in high-income settings.^[5] Data on adult-onset strabismus is incomplete due to underreporting and less routine screening in older populations, with prevalence estimates of 0.90% in U.S. adults as of a 2025 study using the All of Us database but likely underestimated due to healthcare access disparities.^[79] Historically, strabismus has been recognized since ancient times, with descriptions dating back to antiquity in Greek medical texts attributing it to anatomical or obscure causes, while modern epidemiological data emerged from 20th-century population studies establishing its 2% to 5% incidence.^[80]^[69]

References

[1]
Strabismus: MedlinePlus Medical Encyclopedia
Jul 9, 2024 · 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.
[2]
Strabismus (Eye Misalignment): Symptoms, Causes & Treatment
Strabismus (eye misalignment) is a condition in which one eye is turned in a direction that's different from the other eye.
[3]
What is strabismus and how common is it?
Nov 7, 2024 · Strabismus is any misalignment of the eyes. It is estimated that 4% of the US population has strabismus.
[4]
Genetics of strabismus - Frontiers
The prevalence of strabismus is approximately 2%–4% in the pediatric population (22–24), but the prevalence varies based on geographical regions and strabismus ...Missing: symptoms | Show results with:symptoms
[5]
Strabismus - StatPearls - NCBI Bookshelf
Nov 13, 2023 · Strabismus, often called "crossed eyes," is a common visual disorder affecting millions worldwide. This condition disrupts the normal alignment of the eyes.
[6]
Strabismus | Johns Hopkins Medicine
also known as hypertropia and crossed eyes — is misalignment of the eyes, causing one eye to deviate inward (esotropia) toward the nose, or outward ...
[7]
Strabismus (crossed eyes) - American Optometric Association (AOA)
Crossed eyes, or strabismus, is a condition in which both eyes do not look at the same place at the same time. It usually occurs due to poor eye muscle ...
[8]
Crossed-Eyes (Strabismus) | Children's Hospital of Philadelphia
Strabismus, a misalignment of the eyes, is one of the most common eye problems in children, affecting approximately 4 percent of children under the age of six ...Missing: prevalence | Show results with:prevalence
[9]
Strabismus - Heterotropia | Stanford Health Care
Strabismus (say "struh-BIZ-mus") is a vision problem in which both eyes do not look at the same point at the same time.<|control11|><|separator|>
[10]
What Is Adult Strabismus? - American Academy of Ophthalmology
Sep 9, 2024 · Adult strabismus (crossed eyes) is when your eyes are not lined up properly and they point in different directions.
[11]
Tutorial: Binocular Vision
Normal Binocular Single vision requires: Clear Visual Axis leading to a reasonably clear vision in both eyes; The ability of the retino-cortical elements to ...
[12]
Strabismus, Binocular Vision and Adaptations - AmblyoPlay
Jun 29, 2020 · In individuals with strabismus, the misalignment of the eyes disrupts binocular vision. When the eyes are misaligned, each eye sends a different ...
[13]
Association of Strabismus With Functional Vision and Eye-Related ...
Mar 26, 2020 · Strabismus (ocular misalignment) is a common pediatric eye condition, affecting between 2% to 4% of developmentally normal children and most ...
[14]
Strabismus (Squint) Classification and Management - Patient.info
Concomitant (non-paralytic) or incomitant (paralytic): strabismus can be concomitant, where the size of the deviation does not vary with direction of gaze ...
[15]
Pattern Strabismus - American Academy of Ophthalmology
Dec 28, 2020 · Vertically incomitant pattern strabismus is used to describe the type of strabismus wherein the amount of horizontal deviation changes ...
[16]
A study of heredity as a risk factor in strabismus | Eye - Nature
Aug 27, 2002 · Several studies have shown a much higher prevalence of strabismus in families with strabismic members, suggesting a genetic component.
[17]
Missense mutation in the PAX6 gene can cause a complex mild ...
Aug 3, 2021 · We recommend considering PAX6 as a candidate gene in the diagnostic screen for familial concomitant strabismus in order to avoid missed diagnosis of the mild ...
[18]
Strabismus: Infantile Esotropia - American Academy of Ophthalmology
Jan 28, 2016 · The incidence of dissociated strabismus is reported to occur in 60% to 80% of patients with infantile esotropia.9 DVD is treated with superior ...
[19]
Strabismus - Children's Health Issues - Merck Manuals
In children 6 months of age or older, strabismus is often caused by a refractive error (excessive farsightedness [hyperopia]) or an imbalance in the pull of ...
[20]
Risk Factors for Strabismus (Crossed Eyes) - Stanford Health Care
Adults may develop strabismus from eye or blood vessel damage. Loss of vision, an eye tumor or a brain tumor, Graves' disease, stroke, and various muscle and ...Missing: developmental | Show results with:developmental
[21]
Strabismus: | Contemporary Pediatrics
Mimics of CN VI palsy include orbital lesions and fractures, thyroid disease, myasthenia gravis (rare in children), and Duane syndrome.
[22]
Hypertropia - EyeWiki
Jul 30, 2025 · Thyroid Eye Disease. Thyroid eye disease leads to enlargement of the extraocular muscles and restrictive strabismus. Although any extra-ocular ...
[23]
Strabismus: Duane Retraction Syndrome
Jul 22, 2020 · Duane retraction syndrome (DRS) is a unique restrictive variety of strabismus that is present from birth. It is characterized by co-contraction of the medial ...
[24]
Strabismus and the Oculomotor System: Insights from Macaque ...
Disrupting binocular vision in infancy leads to strabismus and oftentimes to a variety of associated visual sensory deficits and oculomotor abnormalities.
[25]
Neuro-ophthalmology Illustrated Chapter 13 – Diplopia 1 – Basics
Nov 13, 2019 · Hering's law of equal innervation states that during conjugate eye movements, the paired yoke muscles of each eye receive equal innervation so ...
[26]
Amblyopia and Binocular Vision - PMC - PubMed Central - NIH
Typically, amblyopia is clinically defined as reduced visual acuity accompanied by one or more known amblyogenic factors, such as strabismus, anisometropia, ...
[27]
Congenital Fibrosis of the Extraocular Muscles (CFEOM) - EyeWiki
Oct 1, 2025 · Congenital fibrosis of the extraocular muscles (CFEOM) is a rare congenital syndrome characterized by non-progressive unilateral or bilateral ...
[28]
Ocular Torticollis - EyeWiki
Sep 19, 2025 · Ocular torticollis is defined by abnormal head posture as a compensatory mechanism for an ocular abnormality.
[29]
Introduction to Amblyopia - American Academy of Ophthalmology
Oct 21, 2015 · The prevalence of amblyopia worldwide is approximately 1%–5%.4-7 The World Health Organization (WHO) estimates 19 million children less than 15 ...
[30]
Amblyopia - StatPearls - NCBI Bookshelf - NIH
Feb 12, 2024 · It is commonly referred to as "lazy eye." The global prevalence of this condition ranges from 1% to 2%. The causes and risk factors of amblyopia ...
[31]
Stereopsis and Tests for Stereopsis - EyeWiki
Mar 31, 2025 · Patients with strabismus exhibit tropias, which manifest as binocular misalignments. If these tropias are present from an early age, stereopsis ...Introduction · Depth perception · Quantification of stereopsis · Tests for stereopsis
[32]
Anomalous Retinal Correspondence - EyeWiki
Jul 28, 2025 · Anomalous retinal correspondence was first described by Johannes Peter Müller in 1826 – today much more is known.
[33]
Strabismus and Mental Health in Children
May 1, 2022 · Children with strabismus had higher odds of having anxiety, depression, bipolar disease, and schizophrenia than did those without eye diseases.
[34]
Strabismus Associated With Mental Health Conditions in Adults
Apr 16, 2024 · A higher prevalence of anxiety (32% vs 14%; 95% CI, 15%-19%), depression (33% vs 14%; 95% CI, 17%-20%), substance use (3% vs 1%; 95% CI, 1%-3%) ...
[35]
Evaluation and management of strabismus in children - UpToDate
Jan 6, 2025 · Outline · History · General physical examination · Eye examination · - Corneal light reflex · - Cover test · - Cover/uncover test · - Brückner test.
[36]
None
Summary of each segment:
[37]
Evaluating squints in children - RACGP
The four tests used to screen for stra-bismus are the light reflex test, the red reflex test, the cover test and the uncover test. Any child diagnosed with ...
[38]
Clinical Examination of Ocular Alignment and Binocular Vision in ...
Jun 5, 2019 · The Brückner test screens for strabismus, anisometropia, media opacities, abnormal pupil reactions, and fundus anomalies near the visual axis.
[39]
Cycloplegic refraction in children - PMC - PubMed Central - NIH
Cycloplegic refraction makes it possible to accurately measure a child's refractive error and provide appropriate correction.
[40]
Accommodative Esotropia - EyeWiki
Apr 16, 2025 · Diagnosis. Perform a comprehensive ophthalmic exam, including assessment of ocular alignment at distance and near, a cycloplegic refraction, ...
[41]
Strabismus: Accommodative Esotropia
Jan 20, 2016 · If the distance esotropia is still noted to be high, a repeat cycloplegic refraction may be necessary. If there continues to be a significant ...
[42]
The 8-Point Eye Exam - American Academy of Ophthalmology
Jun 11, 2023 · At the slit lamp, variations of a 90D or 78D lens can provide a magnified view to assess subtle changes of the nerve, vessels and macula. 20D ...
[43]
Management of strabismus in thyroid eye disease - PMC
Dec 19, 2014 · Thyroid function tests are usually diagnostic, but a small proportion of patients with TED have normal thyroid function tests.
[44]
When to Image a Patient With Strabismus
Nov 28, 2017 · High-resolution MRI of the orbits can help confirm the diagnosis, if in doubt, and will show symmetric or asymmetric downward displacement of ...
[45]
High-Resolution Magnetic Resonance Imaging Demonstrates ...
High-resolution MRI can directly demonstrate pathology of CN3 and CN6 and affected EOM atrophy in strabismus caused by CN palsies.
[46]
Adult Strabismus Preferred Practice Pattern® - Ophthalmology
Strabismus is likely to be associated with diplopia and, in some cases, a compensatory head posture (i.e., ocular torticollis, often a chin-up position in this ...
[47]
ELECTROMYOGRAPHY IN STRABISMUS - PMC - NIH
Electromyography of the human extraocular muscles is a new research tool designed to elucidate many problems in ocular physiology.
[48]
Visual evoked potential importance in the complex mechanism ... - NIH
Abstract. To compare the visual evoked potential (VEP) responses of amblyopic eyes with VEP responses of sound eyes in amblyopic children.
[49]
Strabismus in Thyroid Eye Disease - EyeWiki
Sep 19, 2025 · Before surgery is considered, it is recommended for patients to achieve stabilization in the degree of strabismus and thyroid function tests.Disease Entity · Disease · Diagnosis · Management
[50]
Genetics of strabismus - PMC - NIH
Jul 20, 2023 · 2. Population differences. The prevalence of strabismus is approximately 2%–4% in the pediatric population (22–24), but the prevalence varies ...
[51]
Accommodative Esotropia - EyeWiki
Apr 16, 2025 · Spectacle correction is the initial treatment for accommodative esotropia. The full cycloplegic correction is usually given initially. This ...
[52]
https://eyewiki.aao.org/Accommodative_Esotropia
[53]
Strabismus in Children - American Academy of Ophthalmology
Nov 13, 2024 · One of the most common reasons is if the child is nearsighted or farsighted. If a child's vision is blurry because of nearsightedness or ...Missing: developmental | Show results with:developmental
[54]
Botulinum Toxin Use In Strabismus - EyeWiki
Technique · EMG: Apply the EMG electrodes to the patient's forehead. · Apply topical anaesthesia to the ocular surface (e.g. oxybuprocaine) · Ensure assepsia of ...
[55]
Strabismus Surgery, Horizontal - EyeWiki
General. The treatment of strabismus may consist of glasses, patching, prisms, eye exercises and/or eye muscle surgery. These may be utilized alone or in ...
[56]
Strabismus Surgery, Cyclovertical - EyeWiki
Nov 4, 2024 · Surgical Complications · Hemorrhage · Pupil Dilation · Fat Adherence Syndrome.
[57]
Strabismus Surgery Complications - EyeWiki
May 12, 2025 · Strabismus surgery is very safe and effective, but complications can occur and need to be diagnosed and treated early to optimize post-operative outcome.Intraoperative Surgical Site... · Post-operative Surgical Site... · Conjunctival Scarring
[58]
Reoperation in Horizontal Strabismus and its Related Risk Factors
Reoperation is a disappointing postoperative complication with a percentage of 20% to 40% in esotropic [1, 2] and 23% to 59% among exotropic patients [3]. Based ...
[59]
Prognostic preoperative factors for successful outcome of surgery in ...
Surgery for horizontal strabismus reportedly has a success rate of 60%–80%. However, which preoperative factors are predictive of this success is not clear.
[60]
Amblyopia in children (aged 7 years or less) - PMC - NIH
Amblyopia is commonly regarded as less amenable to treatment after age 7 to 8 years. Although treatment may be effective in older children, recovery of normal ...
[61]
Strabismus: The importance of timely, specialized care - Mayo Clinic
Jan 18, 2019 · A child with any form of strabismus should be seen as soon as possible by an eye specialist to rule out vision loss or a visually dangerous or unexpected cause ...
[62]
Gains beyond cosmesis: Recovery of fusion and stereopsis in adults ...
It is concluded that longstanding strabismic adults with good vision can recover fusion and stereopsis following successful squint surgery.Missing: prognosis | Show results with:prognosis
[63]
Strabismus Surgery for Psychosocial Reasons—A Literature Review
Apr 22, 2024 · Psychosocial symptoms caused by strabismus also include social phobia, social fear, social avoidance (Bez et al. 2009; Xu et al. 2012), and ...
[64]
Surgical treatment for residual or recurrent strabismus - PMC
According to previous reports, the incidence of undercorrection and recurrence after the correction of esotropia varied from 20% to 40%– and the incidence of ...
[65]
Strabismus: misaligned eyes and its treatment - Allied Academies
Routine eye examinations are essential to monitor the progress of strabismus and adjust treatment as needed. Engaging in prescribed vision therapy exercises ...<|control11|><|separator|>
[66]
Non-surgical treatment of strabismus in children: a review of recent ...
Jun 26, 2025 · Non-surgical treatments such as wearing corrective glasses, using adhesive prisms, wearing bifocal lenses, covering therapy, orthoptic exercises ...Abstract · Introduction · Pathogenesis of pediatric... · Non-surgical treatment...
[67]
Strabismic Adults' Expectations of Psychosocial Support From ... - NIH
May 4, 2025 · Strabismic adult patients dealing with the condition's psychosocial burden expect psychosocial ... Psychological Issues Surrounding Strabismus ...
[68]
Global and regional prevalence of strabismus - PubMed
The estimated of pooled prevalence (95% CI) of any strabismus, exotropia, and esotropia was 1.93% (1.64-2.21), 1.23% (1.00-1.46), and 0.77% (0.59-0.95), ...
[69]
Prevalence and Impact of Vision Disorders in U.S. Children
Between 2 and 4 percent of children under the age of 6 years have strabismus, a misalignment of the eyes that can lead to the development of amblyopia. With the ...
[70]
The Danish Rural Eye Study: prevalence of strabismus among 3785 ...
The prevalence of exotropia (XT) was 0.3% (12/3785; 95% CI: 0.2-0.6) and of esotropia (ET) 0.8% (29/3785; 95% CI: 0.5-1.1), resulting in an XT:ET ratio of 1:2. ...
[71]
Prevalence of strabismus and its risk factors among school aged ...
Jul 5, 2021 · The prevalence of strabismus was found to be 3.3% and 2.1% among White and African Americans respectively. The Strabismus, Amblyopia, and ...
[72]
Gender differences in horizontal strabismus: Systematic review and ...
Sep 1, 2023 · Results: Summary statistics showed a nearly identical prevalence of horizontal strabismus (2.558% for males, 2.582% for females), esotropia ( ...
[73]
Female Predominance in Intermittent Exotropia - ScienceDirect.com
Intermittent exotropia was nearly twice as common in girls compared with boys in this defined population. There were, however, no significant historical or ...Missing: congenital | Show results with:congenital
[74]
Strabismus in Premature Infants in the First Year of Life
The incidence of strabismus at 12 months was 43.1% in patients who had anisometropia at 3 months, but only 9.5% in patients without anisometropia at that age.
[75]
Prevalence and associated factors of strabismus in former preterm ...
Dec 2, 2017 · In very preterm infants with low gestational age (GA) and low birth weight the prevalence of strabismus has been reported to be up to 42% [1–8].
[76]
Prevalence of Amblyopia and Strabismus in African American ... - NIH
Strabismus prevalence is higher in older children, and exotropia is more common than esotropia. Amblyopia prevalence in children 30 to 72 months is higher in ...
[77]
https://pmc.ncbi.nlm.nih.gov/articles/PMC7583393/