Pseudoesotropia
Pseudoesotropia refers to the false appearance of esotropia when the visual axes are actually aligned. The appearance may be caused by a flat, broad nasal bridge; prominent epicanthal folds, a narrow interpupillary distance, or a negative angle kappa (see Chapter 7). The observer sees less sclera nasally than would be expected, which creates the impression that the eye is turned in toward the nose. This is especially noticeable when the child gazes to either side. Because no real deviation exists, results of both corneal light reflex testing and cover testing are normal.
Infantile (Congenital) Esotropia
Infantile esotropia is defined as an esotropia that is present by 6 months of age. Some ophthalmologists refer to this disorder as congenital esotropia. However, because the onset is usually not at birth, the term infantile esotropia is more accurate and will be used in this volume.
Variable, transient, intermittent strabismus is commonly observed in the first 2–3 months of life. Also, it is common to see both intermittent esotropia and exotropia in the same infant (termed ocular instability of infancy). This condition should resolve by 3 months of age but can sometimes persist, especially in premature infants. If an esotropia is present after age 2 months, is constant, and measures 30 prism diopters (Δ) or more, it is unlikely to resolve and will probably require surgical intervention.
Patients with infantile esotropia often have a family history of esotropia or strabismus, but welldefined genetic patterns are unusual. Infantile esotropia occurs in up to 30% of children with neurologic and developmental problems, including cerebral palsy, hydrocephalus, and prematurity. Infantile esotropia has been associated with an increased risk of development of mental illness by early adulthood (2.6 times higher compared with controls).
Olson JH, Louwagie CR, Diehl NN, Mohney BG. Congenital esotropia and the risk of mental illness by early adulthood. Ophthalmology. 2012;119(1):145–149.
Pathogenesis
The cause of infantile esotropia remains unknown. The debate regarding its etiology has focused on the implications of 2 conflicting theories. The Worth “sensory” concept proposes that infantile esotropia results from a congenital deficit in a “fusion center” in the brain. According to this theory, the goal of restoring binocularity is futile. In contrast, the Chavasse theory proposes that the primary problem in infantile esotropia is one of motor development, which is potentially curable if ocular alignment is achieved in infancy. Several authors have reported favorable sensory results in infants operated on between 6 months and 2 years of age, and these encouraging results have become the basis for the practice of early surgery for infantile esotropia.
Evaluation
Visual behavior or visual acuity of the 2 eyes can be equal, in which case alternating fixation will be present. Amblyopia is commonly associated, however. If amblyopia is present, a fixation preference can be observed. Cross-fixation, in which a large-angle esotropia is associated with the use of the adducted eye for fixation of objects in the contralateral temporal field, is also frequent (Fig 8-1).
Figure 8-1 Infantile esotropia. (Reproduced from Archer SM. Esotropia. Focal Points: Clinical Modules for Ophthalmologists. San Francisco: American Academy of Ophthalmology; 1994, module 12.)
Versions and ductions are often normal initially. The deviation is comitant and characteristically larger than 30Δ. Overelevation in adduction and dissociated strabismus complex develop in more than 50% of patients, usually after 1–2 years of age. There may be an apparent abduction deficit because of cross-fixation; children with equal vision in both eyes have no need to abduct either eye on side gaze. If amblyopia is present, the better-seeing eye will fixate in all fields of gaze, making the amblyopic eye appear to have an abduction deficit. The infant’s ability to abduct each eye can be demonstrated with the doll’s head maneuver or by observation with either eye patched. The clinician can also hold the infant and spin in a circle, which stimulates the vestibulo-ocular reflex and helps demonstrate full abduction.
Asymmetry of monocular horizontal smooth pursuit is normal in infants up to age 6 months, with the nasal-to-temporal direction less well developed than the temporal-to-nasal. Patients with infantile esotropia have persistent smooth pursuit asymmetry throughout their lives. Fusion maldevelopment nystagmus syndrome (also known as latent and manifest latent nystagmus) is also a commonly associated motility anomaly. Cycloplegic refraction characteristically reveals low hyperopia (1.00– 2.00 diopters [D]).
A severe form of infantile esotropia, referred to as Ciancia syndrome, consists of large-angle esotropia (>50Δ), abducting nystagmus, and mild abduction deficits. Children with this syndrome uniformly use cross-fixation.
Management
Because accommodative esotropia can occur as early as age 4 months, significant hyperopic refractive error should be corrected by prescribing the full cycloplegic refraction. A small-angle esotropia that is variable or intermittent may be more likely to respond to hyperopic correction than would a large-angle or a constant esotropia.
Ocular alignment is rarely achieved without surgery in early-onset esotropia. Previously, it was thought that concurrent amblyopia should be fully treated before surgery. However, it has recently been shown that successful postoperative alignment is as likely to occur in patients with mild to moderate amblyopia at the time of surgery as it is in those whose amblyopia has been fully treated preoperatively. When ocular alignment is achieved earlier, there may be the added benefits of better fusion, stereopsis, and long-term stability.
The goal of surgical treatment of infantile esotropia is to reduce the deviation to orthotropia or as close to it as possible. Ideally, this results in normal vision in each eye and the development of some degree of sensory fusion. Alignment within 8Δ–10Δ of orthotropia frequently results in the development of the monofixation syndrome, characterized by peripheral fusion, central suppression, and favorable appearance. This small-angle strabismus, also known as a microtropia, generally represents a stable, functional surgical outcome even though bifoveal fusion is not achieved; it is therefore considered a successful surgical result. In addition, the child’s psychological and motor development may improve and accelerate after the eyes are straightened, and bonding between infant and parents may improve.
Most ophthalmologists in North America agree that surgery should be undertaken early. The belief is that the eyes should be aligned by age 24 months, preferably earlier, to optimize binocular cooperation. Surgery can be performed in healthy children as early as age 4 months. The Congenital Esotropia Observational Study showed that when patients with a constant esotropia of at least 40Δ present after 10 weeks of age, the deviations are unlikely to resolve spontaneously. Using this as a basis, some surgeons suggest even earlier surgery, with the aim of achieving a superior sensory outcome. Smaller angles can be monitored, as they may improve spontaneously. However, a European multicenter prospective study (ELISS) comparing early versus delayed strabismus surgery showed only a slight improvement in gross binocularity in the early-surgery group (lower amount of suppression), but a higher number of procedures were performed in the early-surgery group to achieve outcomes similar to those of the delayed-surgery group.
Various surgical approaches have been suggested for infantile esotropia. The most common initial procedure is recession of both medial rectus muscles. Recession of a medial rectus muscle combined with resection of the ipsilateral lateral rectus muscle is also effective. Two-muscle surgery spares the other horizontal rectus muscles for subsequent surgery should it be needed, which is not uncommon. For infants with large deviations (>50Δ–60Δ), some surgeons operate on 3 or even 4 horizontal rectus muscles at the time of the initial surgery, or they add botulinum toxin injection to the medial rectus muscle recession. Significant inferior oblique muscle overaction can be treated at the time of the initial surgery. Chapter 14 discusses surgical procedures in detail.
Botulinum toxin injection alone into the medial rectus muscles has also been used as primary treatment of infantile esotropia. Usually, 2–3 injections into each medial rectus muscle are required, and the average time to achieve alignment is longer with this form of treatment (17 months) than with surgery (2 months).
Birch EE, Stager DR, Everett ME. Random dot stereoacuity following surgical correction of infantile esotropia. J Pediatr Ophthalmol Strabismus. 1995;32(4):231–235.
Pediatric Eye Disease Investigator Group. The clinical spectrum of early-onset esotropia: experience of the Congenital Esotropia Observational Study. Am J Ophthalmol. 2002;133(1):102–108.
Simonsz HJ, Kolling GH, Unnebrink K. Final report of the early vs. late infantile strabismus surgery study (ELISSS), a