Commonly referred to as crossed eyes, esotropia is a common type of strabismus in which one or both eyes turn inward toward the nose. It is most often identified in children between the ages of 2 and 4, although it can occur at any age.
The opposite of esotropia is exotropia, which is characterized by eyes that point outward, toward the ears. The degree of esotropia may vary from small-angle (hardly noticeable) to large-angle (very noticeable), and the condition may be characterized as congenital (meaning that the affected person is born with it) or acquired.
What Are The Signs and Symptoms of Esotropia?
The primary sign of esotropia, obviously, is crossing of the eyes. Habitual squinting or constantly rubbing one eye are also common signs. If your child suffers from this condition, he or she may also complain of double vision.
Crossed eyes can be constant or intermittent. A constant esotropia is present all the time, whereas intermittent esotropia may become apparent only when looking at close objects or only when looking at distant objects, or if the affected person is tired or sick. Intermittent esotropia often requires treatment to prevent it from becoming constant.
As indicated above, esotropia is either congenital or acquired. Congenital esotropia (also known as infantile esotropia) is usually detected during the first six months of life. Infants with esotropia are otherwise developmentally and neurologically normal. Acquired (or secondary) esotropia, which develops later in life, can occur for a variety of reasons:
- Accommodative esotropia is eye crossing that results from the focusing efforts of the eyes. It is the most common form of esotropia in children, and it is caused by uncorrected farsightedness (also known as hyperopia). The eyes cross when they converge in an attempt to focus. In accommodative esotropia, the eye crossing may only be evident when your child stares intently at a near object, or when your child is tired or not feeling well. Correcting the hyperopic refractive error with eyeglasses will usually fix the deviation.
- Non-accommodative esotropia is often associated with an underlying disorder. Early surgical correction appears to benefit children with this condition more than vision correction with eyeglasses.
- Acute esotropia is the sudden development of crossed eyes from no apparent reason in a school-aged or older child with previously normal vision. Immediate evaluation of the child with acute esotropia is necessary to determine the underlying cause. Among the possible causes are a few potentially life-threatening conditions such as meningitis, encephalitis, and head trauma.
- Mechanical esotropia is caused by a problem with the intraocular muscles. The intraocular muscles can become restricted or tightened by disease (like thyroid myopathy, for example), or they may be physically obstructed as a result of a blowout fracture (a blowout fracture is a fracture of the walls of the eye’s orbit—in layman’s terms, the eye sockets in the skull). Mechanical esotropia may be seen in children with Duane syndrome, an eye muscle disorder that can prevent outward movement of the eye (toward the ear).
- Sensory esotropia: A person with this condition suffers from reduced visual acuity in one eye, which hinders or disrupts the process of fusion in normal binocular vision (binocular vision is the coordination of both eyes so that the separate and slightly dissimilar images seen by each eye are appreciated as a single image). Sensory esotropia occurs most frequently in children younger than 5 or 6.
- Consecutive esotropia: This may occur after surgical overcorrection of an exotropia. Consecutive esotropia may result in a condition called amblyopia (lazy eye) and loss of normal binocular vision in young children and diplopia (double vision) in adults.
What Causes Esotropia?
Crossed eyes can be hereditary, although it may occur differently in different family members. It is also associated with prematurity and various neurological and genetic disorders. Farsightedness is the most common vision problem associated with esotropia.
Some systemic disorders, such as hyperthyroidism and diabetes, cause ocular misalignment. The appearance of crossed eyes in an infant is not always a sign of esotropia; it can be a result of the shape of the eyelids or nasal bridge, and as the infant grows, the misalignment goes away. This is called pseudostrabismus.
How Is Esotropia Diagnosed?
Infants and children with suspected esotropia are typically evaluated by a pediatric ophthalmologist or optometrist, who will review the child’s medical and family histories and then perform an examination to determine the child’s visual acuity.
This includes an evaluation of the general health of the eyes and their refractive state (that is, whether the child is farsighted, nearsighted, or has astigmatism). The eyes will be dilated with eye drops to determine the degree of farsightedness.
The ophthalmologist or optometrist will pay close attention to whether the acuity is equal in both eyes or if one eye is stronger than the other. If there is a strong preference for one eye over the other, amblyopia may occur. Amblyopia occurs when one eye fails to properly communicate visual images to the brain, and it is best treated at an early age.
It can sometimes be treated by patching the stronger eye, but in some cases more aggressive methods of treatment are necessary. If ocular misalignment is detected, the degree of misalignment is measured so that the child can be fitted with the appropriate glasses.
How is Esotropia Treated?
Initial treatment of esotropia may involve the prescription of eyeglasses or contact lenses to correct the child’s farsightedness. Glasses should be worn all the time. Children whose eyes cross even when they are wearing glasses or contact lenses may benefit from a bifocal lens.
Surgery is rarely necessary, but may be considered if eye glasses fail to straighten the eyes. Surgery does not eliminate the need for glasses; it simply reduces the degree of eye crossing. The goals of treatment are to re-establish ocular alignment, maximize binocular vision, relieve any double vision, and manage any associated amblyopia.
If amblyopia is present and surgery is being considered, it is best to address the amblyopia with eye-patch therapy before surgery is performed.
What Can I Do To Prevent Esotropia From Developing?
Esotropia cannot be prevented, but complications resulting from it can be prevented if the problem is detected early and treated properly. Children should be monitored closely during infancy and through the preschool years to detect potential eye problems, especially if a relative has strabismus.
In the United States, children are typically screened for eye health before they are six months old, and thereafter at each check-up with their pediatrician or family practitioner. A thorough eye examination by an ophthalmologist or optometrist is recommended when the child is between the ages of 3 and 5.