Ophthalmology – Esotropia: Comitant

Comitant esotropia is a form of strabismus in which one eye deviates inward toward the nose and the angle of deviation remains approximately the same in different positions of gaze. The deviation may be intermittent or constant. Major forms include accommodative, nonaccommodative, sensory, congenital/infantile, consecutive, and cyclic esotropia. Rarely, a seemingly comitant esotropia may occur in association with ocular myasthenia gravis or thyroid eye disease.

Esotropia is relatively common in childhood. One study reported an incidence of approximately 111 per 100,000 individuals younger than 19 years, while the prevalence of esotropia is approximately 2% among children younger than 6 years. Risk factors include hyperopia, prematurity, cerebral palsy, seizure disorders, developmental delay, and poor vision in one or both eyes. Poor vision can interfere with binocular fusion and produce sensory esotropia.

The genetic basis is probably multifactorial, involving both genetic and environmental influences. A positive family history is particularly common in accommodative esotropia. When sensory esotropia occurs because of an inherited ocular disorder, the inheritance pattern of the underlying condition may also be relevant.

Pathophysiology and Etiology

In many patients, no specific structural abnormality of the extraocular muscles, orbit, or cranial nerves can be demonstrated. In accommodative esotropia, hyperopia requires increased accommodation to produce a clear retinal image. Because accommodation is physiologically linked to convergence, excessive accommodative effort produces excessive convergence and inward deviation of the eyes.

Early recognition and correction of significant hyperopia may decrease the risk or severity of accommodative esotropia. Once accommodative esotropia develops, consistent use of the prescribed hyperopic correction is important because persistent uncorrected deviation may eventually acquire a nonaccommodative component.

Sensory esotropia results from impaired vision that disrupts normal binocular fusion. Causes can include cataract, retinal disease, optic nerve abnormalities, and, importantly in children, conditions such as retinoblastoma.

Acute-onset comitant esotropia deserves particular attention. Although many cases are benign, acute esotropia associated with neurologic symptoms or other atypical findings can occasionally accompany intracranial disease, including tumors, Chiari malformation, hydrocephalus, or other neurologic abnormalities.

Common associated findings include amblyopia, hyperopia, nystagmus, developmental disorders, and cerebral palsy.

Diagnosis

In children, esotropia is commonly first noticed by the parents. The deviation may initially be intermittent and subsequently become constant. Adults and older children with acute-onset esotropia may complain of diplopia. The history should address the age and circumstances of onset, frequency of deviation, prematurity, developmental or neurologic abnormalities, family history of strabismus, and any history of reduced vision.

A complete ophthalmic examination is essential. Visual acuity should be assessed in each eye to identify amblyopia or sensory visual loss. Ocular alignment is measured at both distance and near and in multiple positions of gaze to confirm that the deviation is comitant.

A cycloplegic refraction is particularly important because unrecognized hyperopia may be responsible for the esotropia. In some children, strong cycloplegia may be necessary to reveal the full amount of latent hyperopia. Stereoacuity and binocular function should also be evaluated.

The relationship between accommodation and convergence should be assessed. Patients with a high accommodative convergence/accommodation (AC/A) ratio characteristically have substantially greater esotropia at near than at distance and may require additional near correction.

Laboratory investigations are not routinely necessary. When ocular myasthenia is suspected, appropriate antibody testing and neurologic evaluation may be indicated. Thyroid function testing is appropriate when thyroid eye disease is suspected.

MRI of the brain and/or orbits is not routinely required for typical longstanding childhood comitant esotropia. Neuroimaging should be considered for acute-onset esotropia accompanied by neurologic abnormalities, atypical ocular motility findings, papilledema, headache, or other concerning features.

The differential diagnosis includes pseudoesotropia, particularly from prominent epicanthal folds, as well as incomitant esotropia, cranial nerve palsies, ocular myasthenia gravis, and thyroid eye disease.

Treatment

Treatment depends on the underlying type of esotropia. In accommodative esotropia, the primary treatment is correction of the full cycloplegic hyperopic refractive error with glasses or contact lenses. The objective is to reduce accommodative effort and thereby decrease excessive accommodative convergence.

Patients with a high AC/A ratio and persistent near esotropia may benefit from bifocal correction in selected circumstances. Children should be encouraged to wear their prescribed glasses consistently.

Associated amblyopia must be treated, usually with appropriate optical correction followed, when necessary, by patching or pharmacologic penalization of the better-seeing eye. Amblyopia therapy improves vision but does not necessarily eliminate the underlying strabismus.

Medication generally has no role in ordinary comitant esotropia. Medical treatment is directed toward specific underlying disorders, such as myasthenia gravis, when present. Vision therapy is not considered an established treatment for typical comitant esotropia.

Strabismus surgery is considered when a clinically significant nonaccommodative deviation persists despite appropriate refractive and amblyopia treatment. Surgical options include unilateral recession-resection procedures or, commonly, bilateral medial rectus recession. Surgery is generally performed as an outpatient procedure.

Follow-up and Prognosis

Follow-up depends on the patient’s age, visual acuity, refractive error, and stability of alignment. Children with accommodative esotropia require regular monitoring of visual acuity, ocular alignment, refractive error, binocular function, and amblyopia. Follow-up every several months is often appropriate during active childhood management.

Parents should understand the distinction between amblyopia and strabismus. Amblyopia refers to impaired visual development, whereas strabismus describes ocular misalignment. In accommodative esotropia, parents should also understand that the eyes may cross when the glasses are removed even when treatment is working appropriately.

The prognosis of accommodative esotropia is generally good when identified and treated early. Some patients continue to require hyperopic correction long term, while others become less dependent on their correction as they grow. A proportion develop a persistent nonaccommodative component and ultimately require strabismus surgery.

The major complication is amblyopia. Strabismus surgery can result in residual esotropia or overcorrection producing consecutive exotropia. Less common surgical complications include infection, hemorrhage, slipped or lost extraocular muscles, and, very rarely, significant visual loss.