Infantile esotropia is a specific form of strabismus (crossed eyes) that appears within the first six months of a child’s life. While some infants experience temporary and harmless eye drifting, infantile esotropia involves a large and constant inward misalignment of one or both eyes. The term “congenital esotropia” is sometimes used, but this is often inaccurate as the condition is rarely present at birth, typically developing between three and six months of age.
Identifying Infantile Esotropia
The most prominent sign of infantile esotropia is a consistent and significant inward deviation of an eye that is readily apparent. In some cases, infants may adopt a behavior called cross-fixation, where they use their left eye to look to the right and their right eye to look to the left. This can give the impression that the baby has difficulty moving their eyes outward, though the range of motion is normal.
It is important to distinguish this true misalignment from pseudoesotropia, which is the illusion of crossed eyes in an infant who has properly aligned eyes. This appearance is caused by certain facial features, such as a wide, flat nasal bridge or prominent skin folds at the inner corner of the eyelids. These features can obscure the white part of the eye near the nose, making the eyes seem turned inward.
The Diagnostic Process
When infantile esotropia is suspected, a pediatric ophthalmologist will perform non-invasive tests to confirm the diagnosis. A key part of the examination is the Hirschberg test, where the specialist shines a penlight at the infant’s eyes. The location of the light’s reflection on the corneas helps determine alignment; in esotropia, the reflection in the turned eye will be displaced outward.
Another common procedure is the cover-uncover test. The ophthalmologist covers one of the infant’s eyes and observes the movement of the uncovered eye. If the uncovered eye moves outward to fixate on a target, it indicates a manifest strabismus like esotropia.
To get a complete picture, the specialist performs a cycloplegic refraction. This involves using eye drops to temporarily relax the focusing muscles, allowing for an accurate measurement of any refractive errors like farsightedness (hyperopia). While moderate hyperopia is common, it is not the direct cause of infantile esotropia.
Treatment Approaches
The definitive treatment for the eye misalignment in infantile esotropia is surgery. The procedure involves adjusting the tension of the horizontal muscles attached to the eye. For esotropia, the surgeon weakens the medial rectus muscles, which pull the eye inward, through a recession procedure. This involves detaching the muscle and reattaching it further back on the eyeball to reduce its pulling power.
This surgery is usually performed on both eyes to ensure they are balanced, even if only one eye appears to be turning. Studies show that performing surgery before age two can lead to better outcomes for vision development. While a single surgery is often successful, some children may require additional procedures later to refine the alignment.
Unlike other forms of esotropia, glasses are not the primary treatment for correcting the inward turn of infantile esotropia. While glasses may be prescribed if the infant has a significant refractive error, they do not resolve the underlying muscle imbalance. Other treatments, such as patching one eye, are not used to straighten the eye but to treat associated conditions that can develop.
Associated Vision Conditions
The constant inward turning of an eye in infantile esotropia can lead to other vision problems because the brain receives two different images. To avoid double vision, the brain may start to ignore the input from the misaligned eye. This can result in amblyopia, commonly known as “lazy eye,” where the vision in the suppressed eye does not develop properly. Amblyopia occurs in about half of children with this condition and is a primary reason why early treatment is recommended.
Beyond amblyopia, children with infantile esotropia can develop more complex eye movement patterns. One such condition is Dissociated Vertical Deviation (DVD), where the non-fixing eye drifts upward, particularly when the child is tired or inattentive. Another potential issue is inferior oblique overaction, which causes the eye to move excessively upward when it looks inward. These associated conditions highlight that infantile esotropia is a complex disorder of ocular motility.