The goal of this study is to determine whether corrective surgery done earlier than the current standard can better improve the visual and eye movement deficits in children with infantile esotropia (crossed eyes in infancy).

While there is a uniform agreement among pediatric ophthalmologists that most infantile esotropia requires surgical correction, the proper timing of surgery is controversial. In North America, the typical age at surgery ranges from 11-18 months. Unfortunately, despite successful surgical realignment of the eyes, the sensory and eye movement deficits often persist. Recently, some pediatric ophthalmologists have advocated earlier surgery. The rationale for early surgery stems from animal and human research showing that early realignment of the eyes within an early critical period allows normal development of the sensory and eye movement systems.

Inclusion Criteria:

1. onset of esotropia after 10 weeks of age;
2. constant esotropia ≥ 20° (40 prism diopter or PD) at near (1/3 m) on two examinations, separated by 2-4 weeks; and
3. refractive error ≤ +3.00 diopters (far-sightedness).

Exclusion Criteria:

1. gestational age < 34 weeks;
2. birth weight ≤ 1500 g;
3. ventilator treatment in the newborn period;
4. history of meningitis or other major medical event;
5. developmental delay;
6. incomitant or paralytic strabismus;
7. manifest nystagmus or head bobbing;
8. prior eye muscle surgery;
9. prior treatment of amblyopia or spectacle correction for refractive errors;
10. presence of structural ocular anomalies.

Patients with infantile esotropia will be enrolled from The Hospital for Sick Children in Toronto. Infants with characteristics that indicate low likelihood of spontaneous resolution will be studied.