eMedicine Specialties > Ophthalmology > Extraocular Muscles

Esotropia, Infantile

Author: Vicente Victor D Ocampo, MD, Consulting Staff, Department of Ophthalmology, Asian Hospital and Medical Center, Philippines
Coauthor(s): C Stephen Foster, MD, FACS, FACR, FAAO, Clinical Professor of Ophthalmology, Harvard Medical School; Consulting Staff, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary; Founder and President, Ocular Immunology and Uveitis Foundation, Massachusetts Eye Research and Surgery Institution
Contributor Information and Disclosures

Updated: Feb 27, 2007

Introduction

Background

Strabismus is one of the most relevant health problems of the world, and infantile esotropia is perhaps the most visually significant yet is the least understood. Infantile esotropia is the inward deviation of the eyes noted before the patient reaches age 6 months. To date, its exact cause has yet to be identified, and an effective treatment strategy is yet to be formulated.

Pathophysiology

The exact cause of infantile esotropia remains unknown. While some opine that esotropia is due to excessive tonic convergence, few agree on what accounts for such conditions. Worth strongly believed that esotropia is an inborn and irreversible defect of fusion. As such, it is a primary dysfunction in the normal development of binocular sensitivity. This was countered by Chavasse who asserted that the neural components necessary for normal binocular vision are present in strabismic individuals at birth, but the development of fusion is eventually impeded by abnormalities of optical input (eg, monocular cataracts) or muscular output (eg, cranial nerve palsies).

The origins of infantile esotropia are just as undefined. A few authors have implicated practically everything from and between the extraocular muscles to the visual cortex in the causation of infantile esotropia.

Although understanding the mechanisms behind infantile esotropia has come a long way, there is still a lot of ground to cover to unearth and clearly understand such an elusive condition.

Frequency

United States

Strabismus is one of the most prevalent ocular problems among children, affecting 5 in every 100 US citizens, or some 12 million people in a population of 245 million. Of this, infantile esotropia is thought to affect about 1% of full-term, healthy newborns and a much higher percentage of newborns with perinatal complications due to prematurity or hypoxic/ischemic encephalopathy.

In an attempt to determine whether esotropia is present at birth or develops later in infancy, Nixon et al observed 1,219 alert infants in a normal newborn nursery at a city hospital and noted that only 40 babies (3.2%) had esotropia (intermittent esotropia in 17 patients, with 14 patients varying between esotropia and exotropia, and 9 patients with variable esotropia). In addition, no infant displayed characteristic features of infantile esotropia. As such, infantile esotropia is not believed to be connatal but rather develops in the first few weeks or months after birth.

Greenberg et al reported an annual age- and gender-adjusted childhood esotropia incidence of 111 per 100,000 patients younger than 19 years. This rate corresponds to a cumulative prevalence of approximately 2% of all children younger than 6 years, with a significant decrease in older ages. The incidence of childhood esotropia from this population-based study is comparable to the prevalence rates among Western populations. Esotropia is most common during the first decade of life, with the accommodative and acquired nonaccommodative forms occurring most frequently.

Mortality/Morbidity

Exotropia in infancy is believed to be associated with an increased prevalence of coexisting neurologic, ocular, and craniofacial abnormalities. To a lesser degree, infantile esotropia also has been associated with a high prevalence of systemic disorders, including prematurity, neurologic, and genetic disorders. Reports of coexisting brain lesions (eg, periventricular leukomalacia, enlargement of the lateral ventricles with hypoplasia of the corpus callosum, myelination delay at the anterior horn adjacent of the lateral ventricles) have been published.

Age

By definition, infantile esotropia is seen in infants before age 6 months.

Clinical

History

Infantile esotropia typically is not present at birth but rather develops in the early months of infancy. Often, the child manifests with chronic inward deviation (esodeviation) of the visual axes at age 2-4 months. This may be preceded by several weeks of transient episodes of misalignment, accounting for the often mentioned history of eyes crossing at birth.

Classic infantile esotropia is constant and involves a large angle of deviation exceeding 20 prism diopters (PD) on corneal light reflex measurement. As a rule, children with constant esotropia of greater than or equal to 40 PD in the first 2-4 months of life rarely resolve spontaneously to orthophoria. In addition, reduction of the angle of deviation below 40 PD is uncommon in these patients.

Children with initially smaller angles of deviation (<40 PD) or variable angle esotropia have a slightly better chance of resolution to orthophoria. However, 3 cases with infantile esotropia whose angle of deviation decreased spontaneously to less than 10 PD over a minimum follow-up period of 37 months eventually were observed to develop late complications of infantile esotropia (eg, bilateral inferior oblique muscle overaction, latent nystagmus, dissociated vertical deviation).

Consequently, children who undergo surgical alignment at age 6 months have a higher prevalence of coarse stereopsis than those who are corrected surgically at age 7-15 months.

• Associated clinical findings
  • Infantile esotropia may be associated with a spectrum of clinical presentations, including amblyopia, impaired binocularity, central scotomas, and incomitance.
  • Amblyopia is relatively common in patients with infantile esotropia. Weakley et al stated that amblyopia should be suspected strongly in patients with esotropia and asymmetric inferior oblique activity, specifically in the eye with more inferior oblique overaction.
  • Most clinical evidence suggests that sensory and motor functions are nearly normal if alignment (within 10 PD of orthophoria) is attained within the first 2 years of life. Virtually all patients with infantile esotropia fail to develop normal binocular vision and stereopsis.
    • Mohindra et al reported that children with infantile esotropia corrected with prisms equal in size to the deviation showed some degree of binocularity up to at least 2.5 years, as measured by a Polaroid bar stereogram procedure with 1800 seconds of arc disparity; however, all older patients (>6 y) with a history of infantile esotropia failed the test.
    • On the other hand, studies have shown that compared to an age-matched population, monocular preferential-looking acuity in infantile esotropes was not significantly different during months 3-14 for the preferred eye and during months 3-8 in the nonpreferred eye. Stereopsis and monocular acuity were noted to be significantly lower in the older esotropic patients. These studies showed that deficits in preferential-looking acuity and subsequent amblyopia occur after the onset of fixation preference and that stereoscopic pathways are present and functional in at least some esotropic infants.
  • Central scotomas almost always are identifiable, even in patients with optimal motor alignment and with the highest levels of binocular vision. On the other hand, it had been stated that the inferonasal quadrant of the visual filed is constricted in patients with infantile esotropia as a result of dissociated vertical deviation. Haefliger et al subsequently refuted this statement.
  • Incomitance also may be observed. The most common type is the V-pattern infantile esotropia, wherein esodeviation is greater in downgaze than in upgaze. V-pattern infantile esotropia is attributed largely to overaction of the inferior obliques. The reverse of this type, the A-pattern, also may be noted in infantile esotropes.

Physical

According to Tychsen, infantile esotropes manifest with a constellation of ocular motor signs, as follows:

• Esotropia, with or without strabismic amblyopia
• Pursuit asymmetry
• Latent fixation nystagmus
• Motion visual-evoked potential (VEP) asymmetry and motion perception abnormalities
• A face turn and abduction deficit
• Dissociated vertical deviation

Causes

Both the exact cause and the associated risk factors of infantile esotropia have yet to be identified distinctively. While it strongly is believed that a genetic component exists, a solid basis for linkages among family members still needs to be established. However, several studies have made significant inroads toward establishing a genetic causation for infantile esotropia. Tychsen and Lisberger reported in 1986 that the strabismic patient who had the most severe pursuit/motion processing asymmetry had 2 siblings with infantile esotropia. Furthermore, large-scale investigations have shown that 20-30% of children born to a strabismic parent eventually will develop strabismus themselves.

The added risks of perinatal complications (eg, prematurity, birth injury, low birth weight) to infantile esotropia have been investigated, yielding equivocal, if not contrary, results.

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