If the child is less than 2 months old and the eyes cross occasionally, and there are no visible abnormalities of the eyes, the child should be rechecked after 2 months of age. Patients with constant crossing at any age, or intermittent crossing that persists after 2 months of age, should be referred to a pediatric ophthalmologist.

What Shouldn’t Be Missed

Although uncommon, abnormalities of the eye such as cataract or retinoblastoma may initially present with strabismus (secondary to decreased vision). The prognosis for these disorders is greatly improved with prompt treatment. Any child with strabismus and an abnormal red reflex should be referred immediately.

• 1. Normal newborn (physiological intermittent strabismus of the newborn). Intermittent eye crossing is relatively common in the first 1 to 2 months of life. The angle of eye crossing may be quite large, but the duration is brief (a few seconds). This resolves in most infants by 2 months of age.
  
• 2. Pseudostrabismus. Normal infants have a wider and flatter nasal bridge than adults. When an infant looks to the side, this tissue may block visualization of the white nasal sclera in the eye that is turned toward the nose, while the sclera remains visible in the other eye. This asymmetry creates an optical illusion that makes it appear as if one eye is crossing. Examination of the corneal light reflex reveals that the eyes are straight (Figure 9–1).
  
• 3. Infantile esotropia. True eye crossing (esotropia) is usually not present at birth. It most often begins around age 2 months. Initially it may occur intermittently, but usually progresses rapidly to constant crossing. When the infant’s eye crosses, the brain stops paying attention to the visual information from the eye. This may cause amblyopia if one eye is constantly crossed. Some children spontaneously alternate fixation between the eyes (alternate fixation) (Figure 9–2A and B). Binocular vision cannot develop in children with infantile esotropia unless the crossing is corrected. Early surgical realignment of the eyes improves the outcome. Infantile esotropia is more common in children with developmental delay (Table 9–1).
  
• 4. Decreased vision. Any condition that causes decreased vision, particularly if it affects only one eye, may cause a secondary strabismus. In infants, the strabismus in the poorly seeing eye is most commonly esotropia. The list of possible causes includes virtually any ocular disorder that affects vision. Some of these are incurable (such as optic nerve hypoplasia or large retinal colobomas), but some are amenable to treatment (such as cataracts or retinoblastoma). For the latter, early diagnosis and treatment may dramatically improve the prognosis.