Input from two eyes converge on binocular neurons in the visual cortex which are the neural substrate for stereopsis (depth perception).

Maturation of binocular neurons is dependent on ocular alignment early in life.

Childhood strabismus impairs proper ocular alignment and results in permanent loss of stereopsis if proper alignment is not realigned early in childhood development.

Unmanaged pediatric strabismus can cause amblyopia, a decrease in best corrected visual acuity in a health eye.

Vertical strabismus a common symptom in the neurophthalmology practice and may result from several conditions, including skew deviation and acquired fourth nerve palsy.

Skew deviation reflects damage to the supranuclear vestibular pathways and may constitute the initial manifestations of a life-threatening disorder, such as brain stem stroke.

Isolated acquired fourth cranial nerve palsy is often caused by microvascular ischemia and trauma and rarely represents a neurological emergency.

Skew deviation is commonly accompanied by additional ocular motor and neurologic signs that aid in diagnosis.

Accurate clinical differentiation between the strabismus pattern of fourth cranial nerve palsy and secure deviation is critical in the acute setting.

Also known as crossed eyes.

A condition in which the eyes do not properly align with each other when looking at an object.

May also be a cosmetic problem.

85% of adult strabismus patients report that they had problems with work, school, and sports, and 70% say it had a negative effect on self-image.

The eye which is focused on an object can alternate.

The condition may be present occasionally or constantly.

If present during a large part of childhood, it may result in amblyopia or loss of depth perception.

If onset is during adulthood, it is more likely to result in double vision.

Results in the eyes not aiming at the same point in space.

Esotropia refers to eyes crossed.

Exotropia refers to eyes diverged.

Hypertropia refers to eyes vertically misaligned.

Causes include:

Muscle dysfunction, farsightedness, problems in the brain, trauma, infections

Risk factors include:

Premature birth, cerebral palsy, family history.

Frequency about 2% of children.

Strabismus can also be classified by whether the problem is present in all directions a person looks or varies by direction.

Diagnosis may be made by observing the light reflecting from the person’s eyes and finding that it is not centered on the pupil.

Treatment depends on the type of strabismus and the underlying cause.

Treatments include the use of glasses and possibly surgery.

Tests, such as cover testing, can determine the full extent of the strabismus.

Symptoms of strabismus include double vision and/or eye strain.

To avoid double vision, the brain may adapt by ignoring one eye, and may be associated with a minor loss of depth perception.

Patients learn to judge depth and distances using monocular cues.

A constant unilateral strabismus causing constant suppression is a risk for amblyopia in children.

Small-angle and intermittent strabismus are likely to cause disruptive visual symptoms, headaches and eye strain.

Symptoms may include an inability to read comfortably, fatigue when reading, and unstable vision.

People with noticeable strabismus may experience psychosocial difficulties.

Strabismic children commonly exhibit behaviors of inhibition, anxiety, and emotional distress, often leading to emotional disorders., which are often related to a negative perception of the child by peers.

It interferes with normal eye contact, often causing embarrassment, anger, and feelings of awkwardness, affecting social communication.

Children with strabismus, particularly those with exotropia may be more likely to develop a mental health disorder than normal-sighted children.

Surgical correction of strabismus has a significantly positive effect on psychological well-being.

Risk is increased among those with a family history of the condition and can be seen in Down syndrome, Loeys-Dietz syndrome, cerebral palsy, and Edwards syndrome.

A problem with the extraocular muscles or the nerves controlling the position of the eyes 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 eye to drift up and perhaps slightly inward.

Sixth nerve palsy causes the eyes 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.

Strabismus may cause amblyopia due to the brain ignoring one eye.

Amblyopia is the failure of one or both eyes to achieve normal visual acuity despite normal structural health.

The brain learns how to interpret the signals that come from an eye through a process called visual development.

Visual development occurs during the first seven to eight years of life,

Visual development may be interrupted by strabismus if the child fixates with one eye and rarely or never fixates with the other.

When strabismus is congenital or develops in infancy, it can cause amblyopia.

Stereo blindness may occur with amblyopia

Visual development is impaired when the signal from the deviated eye is suppressed, and causes a failure of the vision in that eye.

Amblyopia may cause strabismus, because of the difference in clarity between the images from the right and left eyes

Impaited visual input may be insufficient to correctly reposition the eyes.

Visual difference between right and left eyes that may be due to asymmetrical cataracts, refractive error, or other eye diseases, can also cause or worsen strabismus.

Accommodative esotropia refers to a form of strabismus caused by refractive error in one or both eyes.

When accommodating to focus on a near object, increased signals sent by cranial nerve III to the medial rectus muscles results in drawing the eyes inward.

This above occurrence is called the accommodation reflex.

The diagnosis can be made by using an examination test such as cover testing or the Hirschberg test to measure strabismus and its impact on vision.

It can be manifest or latent in nature.

A manifest deviation, or heterotropia is present while the patient views a target binocularly, with no occlusion of either eye.

With manifest deviation the patient is unable to align the gaze of each eye to achieve fusion.

A latent deviation is only present after binocular vision has been interrupted, usually by covering one eye.

Intermittent strabismus is a combination of both of these types.

Strabismus may also be classified by the timing of onset: congenital, acquired, or secondary to another pathological process.

Infants are frequently born with their eyes slightly misaligned, and this is typically outgrown by six to 12 months of age.

Overconvergence of the eyes due to the effort of accommodation, occurs mostly in early childhood and is referred to as accomodative esotropia.

Acquired non-accommodative strabismus and secondary strabismus are developed after normal binocular vision has developed.

The onset of strabismus in adults usually results in double vision.

Any disease that causes vision loss may also cause strabismus.

It can be the result from any injury to the affected eye.

Sensory strabismus is due to vision loss or impairment, leading to horizontal, vertical or torsional misalignment or to a combination , with the eye with poorer vision drifting slightly over time.

Sensory strabismus outcome is horizontal misalignment.

The direction of strabismus depends on the patient age at which the damage occurs.

Patients whose vision is lost or impaired at birth are more likely to develop esotropia.

Patients with acquired vision loss or impairment mostly develop exotropia.

Complete blindness in one eye generally leads to the blind eye reverting to an anatomical position of rest.

In many cases no specific cause can be identified, and this is typically the case when strabismus is present since early childhood.

The incidence of adult-onset strabismus increases with age, especially after the sixth decade of life, and peaks in the eighth decade of life.

The lifetime risk of being diagnosed with adult-onset strabismus is approximately 4%.

Classified as unilateral if the one eye consistently deviates, or alternating if either of the eyes can be seen to deviate.

Unilateral strabismus has been observed to result from a severe or traumatic injury to the affected eye.

Strabismus can additionally be classified as follows:

Paretic strabismus is due to paralysis of one or several extraocular muscles.

Nonparetic strabismus is not due to paralysis of extraocular muscles.

Concomitant strabismus is a deviation that is the same magnitude regardless of gaze position.

Noncomitant strabismus has a magnitude that varies as the patient shifts his or her gaze up, down, or to the sides.

Nonparetic strabismus is generally concomitant.

Most types of infant and childhood strabismus are comitant.

Paretic strabismus can be either comitant or noncomitant.

Incomitant strabismus is almost always caused by a limitation of ocular rotations that is due to a restriction of extraocular eye movement or due to extraocular muscle paresis.

Incomitant strabismus cannot be fully corrected by prism glasses, because the eyes would require different degrees of prismatic correction dependent on the direction of the gaze.

Large-angle strabismus refers to the angle of deviation between the lines of sight of the eyes when it is large and obvious, while less severe eye turns are called small-angle strabismus.

Strabismus degree can varies on whether the patient is viewing a distant or near target.

Pseudostrabismus is the false appearance of strabismus, that generally occurs in infants and toddlers whose bridge of the nose is wide and flat, causing the appearance of esotropia due to less sclera being visible nasally.

The primary goal of management is comfortable, single, clear, normal binocular vision at all distances and directions of gaze.

Usually treated with a combination of eyeglasses, vision therapy, and surgery, depending on the underlying reason for the misalignment.

Minor amblyopia detected early can often be corrected an eye patch on the dominant eye and/or vision therapy.

The use of an eye patch, is unlikely to change the angle of strabismus.

In accommodative esotropia, the eyes turn inward due to the effort of focusing far-sighted eyes, and the treatment of this type of strabismus involves refractive correction, via corrective glasses or contact lenses.

In accommodative esotropia surgical correction is considered only if such correction does not resolve the eye turn.

With strong anisometropia, contact lenses may be preferable to glasses because they avoid the problem of visual disparities due to size differences caused by spectacles in which the refractive power is very different for the two eyes.

Treatment of strabismus in a baby may reduce the chance of developing amblyopia and depth perception problems, but randomized controlled trials does not reflect such findings.

Most children eventually recover from amblyopia if they have had the benefit of patches and corrective glasses.

Amblyopia has long been considered to remain permanent if not treated before the age of about seven years, however, recent findings give reason to challenge this view.

Eyes that remain misaligned can develop visual problems.

Prism lenses can also be used to provide some temporary comfort and to prevent double vision from occurring.

Strabismus surgery attempts to align the eyes by shortening, lengthening, or changing the position of one or more of the extraocular eye muscles, and does not remove the need for a child to wear glasses.

Surgery can rarely result in diplopia.

Botulinum toxin therapy for strabismus in patients is most commonly used in adults, but is also used for treating children, in particular children affected by infantile esotropia.

The Botulinum toxin is injected in the stronger muscle, causing temporary and partial paralysis.

Leave a Reply

Your email address will not be published. Required fields are marked *