Squinting or “crossed eyes”, “wall eyes” are conditions of the eye muscles where one or both eyes is deviated inward to outward as opposed to aligning straight to point an object. These include problems with the eye’s shape – such as refractive errors; problems with the way the two eyes combine images – binocular vision disorders; or problems with the nerves and muscles that control eye movement – neurological and muscular disorders. Corrective measures like fabrication of glasses, orthoptic exercises, proper medical intervention may help control the condition and thus may have a good prognosis. 

The absence of strabismus is characterized by terms such as orthophoria, which is perfect alignment without fusional stimulus and orthotropia, which is correct alignment under binocular vision. For example, Heterophoria is a latent deviation that is regulated by fusion while heterotropia is manifest deviation associated with amblyopia. 

Types of strabismus deviations include: 

• Eso-: Eyes turn inside (convergent). 
• Exo-: eye turns outward (divergent). 
• Hyper-: Eye moves upward. 
• Hypo-: Eye moves downward. 
• Incyclo-: It means the eye turns inwards in the direction of the nose, commonly referred to as nasal rotation. 
• Excyclo-: Eye rotates outwards from the vertical position towards the temporal position. 

It is termed congenital if diagnosed within the first 6 months of the baby’s age while it is known as the acquired type if noticed later than 6 months of age. It is described as comitant if the shift in gaze positions is uniform and as incomitant if the deviation is unequal across different positions of gaze. 

Approximately, 5 to 15 million people in the U. S. are affected with Strabismus, this accounts for 2-5% of the entire population. It was established in a National Health Survey that exotropia affects 2.1% and esotropia 1.2% of the surveyed population had from 4 to 74, with a higher probability of having exotropia for older people with ages between 55 and 75.  

Furthermore, approximately 50% of childhood esotropia are partially or fully accommodative, and 10% falls under the non-accommodative esotropia classification. Congenital esotropia occurs in approximately 1 in 100 to 500 children and makes up 8% of all esotropia cases. 1% of esotropia cases. Intermittent exotropia is the most prevalent form of exotropia, and it occurs in 1% of the general populace. 

The specific origin of strabismus is not clear but is associated with the extraocular muscles, cranial nerves and neurological pathways. Two main theories explain its development: 

Claude Worth’s Theory: Literature review points to the conclusion that it seems strabismus happens from the failure of cortical fusion. 

Chavasse Theory: It suggests that, if the motor alignment is disturbed, it results in adverse sensory status and if left uncorrected, causes strabismus. This theory stresses treatment at an early age. 

Squint Squinting is categorized as pseudo strabismus, latent squint and manifest squint Also it includes concomitant squint and incomitant squint. 

Pseudostrabismus: 

Pseudoesotropia is when there is a felxion, prominence of epicanthal fold or negative angle kappa, all of which are common. 

Pseudoexotropia is related most often to hypertelorism or positive angle kappa. 

Heterophoria (Latent Squint): 

Due to anatomical factors, such as unequal orbital position or different distance between the pupils or physiological factors such as increased reception of the accommodative element (esophoria) and decreased reception of the same element (exophoria). Such circumstances that may lead to decompensation include psychiatric disorders, illness, age, or precision work. 

Manifest Squint (Heterotropia): 

• Concomitant Squint: Sensory causes include those which prevent good visual acuity such as refractory errors or optic nerve disease. Motor causes include ocular misalignment because of orbital, muscle, and accommodation troubles. 
• Incomitant Squint: Neurogenic cause is when the cranial nerves are injured, or there are neurological disorders. Myopathic causes occurs due to muscle damage or injury and neural muscle junction disorders such as myasthenia gravis. 

For strabismus, the outcome is generally favorable if diagnosed and managed in childhood. Brief and infrequent eye deviation may be observed in infants but there is no cause for worry. It is therefore normal for binocular coordination to develop at round 3 months and strabismus beyond this age is regarded as pathological. It is important to treat strabismus before the patient has reaches the age of 6 to 8 years because, if left untreated at that age, it causes amblyopia permanent vision loss. 

Referral to an ophthalmologist is recommended if any of the following are observed: 

Abnormality of the pupillary reflex or squinting of the eyes 

Constant esotropia 

Incomitant strabismus 

Abnormal inward turn of the eye persisting at or after the age of 4 months. 

Age Group 

Infants (0 to 12 months): Strabismus is often seen in infants especially during their first few weeks of life, but it is not dangerous at all if it does not continue beyond 3 to 4 months of age.  

Children (1 to 6 years): Amblyopia is commonly detected at a young age, and strabismus can be present in children starting from infancy. The presentation may be the intermittent or constant presentation of deviations.  

Older Children and Adolescents (7 to 18 years): Strabismus develop most of the time since childhood or from early childhood and may develop later in life.  

• Inspection: Look at the position of the eyelids and eyes while the patient is at complete rest. Early signs include any of the eyes moving inwards, outwards, upwards, or downwards as the other eye does not do so. 
• Visual Acuity: Assess visual acuity in the patient by reading prescribed charts according to the patient’s age. It also enables one to identify if there is any impairment of vision from the strabismus, especially in cases of amblyopia. 
• Hirschberg Test: Use a torch and illuminate the patient’s eyes and analyze the resemblance to mirror like surface of the corneas. Abnormal conditions which may cause misalignment may be identified by an unhealthy light reflex. 
• Prism Testing: Since accurate measurements of the angle of deviation through the two lens systems is required, the use of prisms to do so will suffice.  

• Refractive Errors 
• Neurological Disorders 
• Genetic Factors 
• Trauma 
• Systemic Conditions 

Intermittent Strabismus: Often seen occasionally and may not cause huge problems with vision if treated promptly. It can be linked to tasks that demand close attention for extended periods. 

Constant Strabismus: Is usually characterized by a chronic strabismus and can cause amblyopia if the condition is not effectively addressed. 

Incomitant Strabismus: The degree of deviation differs with the gaze direction and may be due to underlying neurological problems. 

Ophthalmology

• Vision Therapy: It is a comprehensive program of eye exercises and activities, which aim at enhancing visual skills and ocular movements. This can help to develop the muscles that are around the eye and at the same time facilitate the brain to focus the eyes.  
• Prism Glasses: There are prism glasses that have lenses which are designed to alter the trajectory of the light entering the eye in a way that makes the images cover up before the eyes of the other eye. This can help to decrease such problems as double vision and other similar problems with vision alignment. 
• Eye Patching: In this technique, the student will be required to put a patch on their stronger eye to encourage the use of the weaker eye. It may enhance the health and vision of the less developed oculo-motor control and can also be effective in controlling the misalignment. 
• Orthoptic Exercises: These are activities that focus on the eye musculature and whose purpose is to correct eye-dominance problems. They are usually prescribed by an ophthalmic technician called orthoptist and they are flexible to individual patient needs. 

Ophthalmology

botulinum toxin: It is mostly referred to as Botox or Dysport which has practical application in strabismus as it paralyzes the eye muscles for a limited time so that the alignment of the eyes can be corrected. It is administered to the eye muscles that are overactive by paralyzing it thereby blocking the release of acetylcholine in the neuromuscular junction. This results in temporary vocal cord paralysis or vocal fold weakness which can assist in minimizing the misaligned muscle activity. 

Ophthalmology

Ecothiopate iodide 0.125% is employed for curing strabismus particularly accommodative esotropia through pharmaceutical intervention. This is the long-acting anticholinesterase which results to miotic effects on the eyes. It also raises peripheral accommodation in consequence of the contraction produced in the sphincter muscle of the iris and the ciliary muscle, thus causing a lessening of the degree of accommodation. 

Ophthalmology

Atropine is commonly administered in the form of ophthalmic solution. The density and the number of applications also vary and depend on the situation and its outcome. Usually this is achieved with atropine 1% or 0. 5% is applied once at night or as the eye care practitioner deems appropriate. 

Surgical Interventions 

• Strabismus Surgery: It refers to adjusting the postures of the eye muscles or the force applied by the muscles to align the two eyes properly. This is accomplished by rehabilitating procedures which either reintegrate, decrease, or enhance the strength of the eye muscles. 

Examples: 

• Recession Surgery: Manipulates the location of the muscle attachment in a way that lessens the power of the staggered muscle’s pull. 
• Resection Surgery: This involves the operation in which one cuts off a segment of the muscle with a view to enhancing the action of the muscle in question. 
• Adjustable Suture Technique: It involves passing adjustable sutures on the eye muscles during the surgery so that the position of muscles can be lined up postoperatively while the patient is still alert. 

Non-Surgical Interventions 

• Botulinum Toxin Injections: It involves the injection of botulinum toxin into specific eye muscles to paralyze them for a temporary period. This can help in decreasing the cases of strabismus and increase alignment. It is prescribed for temporary treatment or as a form of supportive treatment for surgery. It also can be used for patients who cannot undergo surgery or is not recommended for surgery. 
• Vision Therapy: An organized plan of exercises and activities that eye requires to enhance its containers focusing, coordination and alignments. 
• Prism Glasses: Telescopic or bifocal lenses are used where there is a need to move the image to fit the two views eye gets from the two eyes. It is helpful in cases of diplopia and gives some comfort which is helpful when combined with other treatments. 
• Atropine Therapy: Atropine eye drop solution is administered to cause cycloplegia at one’s eye, which in essence limits the extent to which the eyes adjust, thereby assisting in the alignment. 

Ophthalmology

• Evaluation and Diagnosis: Arrange an ophthalmologic examination to assess your child for the type and aetiology of strabismus. 
• Initial Non-Surgical Management: Use simple prescription glasses, vision training, and prescribing prism glasses for management of refractive errors and ocular motor integration. 
• Pharmacological Interventions: Non-surgical methods can be tried but if not effective, botulinum toxin injections or atropine drops can be used or as a preliminary step to surgery. 
• Surgical Intervention: If necessary, then it is possible to perform surgical operations on the muscles that control the position of the eyes. 
• Post-Treatment and Follow-Up: Check progress, modify management and therapy, and ongoing follow up and physical therapy.