Ophthalmology – Esotropia: Infantile

Infantile esotropia is a large-angle, constant inward deviation of the eyes that develops within the first 6 months of life in an otherwise healthy infant. The deviation is usually greater than 35 prism diopters, is typically comitant, and occurs without significant limitation of ocular movements or major refractive error. Amblyopia may be less common at initial presentation than in some other forms of childhood esotropia, but it can develop over time.

Infantile esotropia accounts for approximately 8% of childhood esotropia. Overall, esotropia has been reported to occur in about 111 per 100,000 individuals younger than 19 years, with a prevalence of roughly 2% among children younger than 6 years. A family history of strabismus is an important risk factor.

Pathophysiology

The exact mechanism is not completely understood, but abnormal binocular visual input early in infancy appears to interfere with normal development of ocular alignment and binocular vision. Experimental studies suggest that early disruption of binocular sensory development can produce the characteristic pattern of infantile esotropia and its associated motor abnormalities.

Early restoration of ocular alignment may improve binocular development and reduce the frequency of some later associated findings.

Commonly Associated Conditions

Infantile esotropia is frequently associated with cross-fixation, latent nystagmus, inferior oblique overaction, and dissociated vertical deviation (DVD). Many of these findings are not obvious at initial presentation and may appear later during childhood.

Amblyopia may also occur, particularly if one eye becomes consistently preferred for fixation.

Diagnosis

Parents usually notice persistent inward crossing of one or both eyes at birth or within the first several months of life. The deviation is typically large and constant.

Many infants demonstrate cross-fixation, meaning that the right eye is used to look toward the left side and the left eye is used to look toward the right side. This behavior can give the false impression of impaired abduction.

On examination, the esotropia is typically greater than 35 prism diopters, constant, and approximately equal in different gaze positions. Extraocular movements are otherwise normal.

Refractive error is usually mild and often around the degree of hyperopia expected for age. Significant hyperopia should nevertheless be identified because an accommodative component must be excluded.

Fixation may alternate between the two eyes. If one eye is consistently preferred and the other rarely fixates, amblyopia should be suspected.

An apparent lateral rectus weakness may occur because of cross-fixation. True full abduction can often be demonstrated by covering the fixating eye or by using the Doll’s head maneuver, which activates the vestibulo-ocular reflex.

Imaging

Routine neuroimaging is not necessary in a typical case of infantile esotropia with normal ocular motility and an otherwise normal neurologic examination.

Neuroimaging should be considered when the deviation is accompanied by abnormal ductions or versions, unusual nystagmus, neurologic abnormalities, or other atypical findings.

Differential Diagnosis

Important differential diagnoses include pseudoesotropia, Duane syndrome type I, Möbius syndrome, congenital sixth nerve palsy, nystagmus blockage syndrome, orbital tumors, and other causes of congenital ocular motility restriction.

Pseudoesotropia is especially common in infants with broad nasal bridges or prominent epicanthal folds and must be distinguished from true ocular misalignment.

Duane syndrome should be suspected when limited abduction is associated with globe retraction or narrowing of the palpebral fissure during adduction.

Treatment

The mainstay of treatment is strabismus surgery. The most commonly performed procedure is bilateral medial rectus recession. Very large deviations may require additional surgery involving the lateral rectus muscles.

Before surgery, significant refractive error should be corrected. In particular, substantial hyperopia should be treated to determine whether any accommodative component is present.

Associated amblyopia should also be treated, generally before surgery when possible. Treatment may involve patching or other standard amblyopia therapy.

Timing of Surgery

Achieving good ocular alignment relatively early in life is important for the development of binocular visual function.

Alignment is generally sought before approximately 24 months of age, and some evidence supports even earlier surgical correction in appropriately selected infants.

Spontaneous resolution can occur but is uncommon, particularly with a persistent large-angle deviation.

Follow-up

Long-term follow-up is essential even after successful initial surgery. Children should be monitored for recurrent esotropia, consecutive exotropia, amblyopia, refractive error, inferior oblique overaction, latent nystagmus, and dissociated vertical deviation.

A secondary accommodative component may develop later in childhood and may require glasses even when the initial refractive error was minimal.

Repeat strabismus surgery is relatively common. Up to approximately half of affected children may require another strabismus procedure by around 10 years of age because of recurrent deviation or development of associated ocular motor abnormalities.

Patient Education

Parents should understand that infantile esotropia usually requires long-term ophthalmic monitoring, even when the eyes appear straight after surgery.

They should also understand that treatment has two separate goals: maintaining good vision in each eye and improving ocular alignment and binocular function.

If significant permanent amblyopia remains in one eye, protective polycarbonate spectacles may be recommended to protect the better-seeing eye.

Prognosis

Most children can achieve good visual acuity in both eyes, particularly when amblyopia is detected and treated appropriately.

However, high-grade stereopsis is often limited because normal binocular visual development was disrupted very early in life. Earlier successful alignment generally offers a better chance for useful binocular function.

Complications

The major complications are amblyopia, recurrent esotropia, consecutive exotropia, inferior oblique overaction, latent nystagmus, and dissociated vertical deviation. These late findings may require additional medical, optical, or surgical treatment.