Esotropia is a common eye condition and a specific type of strabismus, the medical term for eye misalignment. The condition is characterized by the inward turning of one or both eyes, often called “crossed eyes.” This misalignment prevents the eyes from focusing on the same point simultaneously, directly impacting binocular vision. Recognizing the underlying cause and classification of esotropia is necessary for effective diagnosis and treatment.
Understanding Esotropia
Esotropia is categorized based on the age of onset and the underlying mechanism driving the inward turn.
Infantile Esotropia
This classification develops within the first six months of life and typically presents as a large, constant angle of deviation. The cause is often unclear but is thought to involve an imbalance in the neurological control of eye movements, rather than a focusing error. This type is usually constant, meaning the eyes are misaligned all the time, and it rarely resolves without intervention.
Accommodative Esotropia
This form usually manifests later in childhood, often between the ages of two and three years. It is directly related to the effort the eye makes to focus, known as accommodation. Because it is tied to focusing, it can often be corrected with glasses that reduce the need for excessive accommodative effort. It is classified as fully accommodative if glasses correct the deviation entirely, or partially accommodative if some misalignment remains.
The condition is also described by its consistency (constant or intermittent) and whether it affects only one eye (unilateral) or switches between them (alternating).
Identifying the Signs
The most obvious sign of esotropia is the visible inward deviation of one or both eyes toward the nose. This misalignment can be noticeable to parents or caregivers, even if it is only intermittent at first. Other observable symptoms may include frequent squinting, blinking, or tilting the head to achieve clearer or single vision.
Older children and adults with acquired esotropia often report double vision (diplopia) because the brain can no longer suppress the image from the misaligned eye. A reduction in depth perception is also common, as the eyes cannot work together to achieve stereopsis. Eye care professionals confirm the diagnosis using specific techniques, such as the cover/uncover test, which reveals the presence and magnitude of the eye turn. The angle of deviation is precisely measured using prisms, quantifying the severity of the misalignment in prism diopters.
Underlying Factors
The misalignment characteristic of esotropia stems from a lack of coordinated control between the six extraocular muscles that surround each eye. While the muscles themselves are often anatomically normal, the issue frequently lies in the neurological pathways responsible for synchronizing their movement. This results in an innervational imbalance between convergence and divergence mechanisms.
Uncorrected farsightedness (hyperopia) is a significant factor strongly associated with accommodative esotropia. To see clearly, a person with hyperopia must exert excessive focusing effort (accommodation). Since the eye’s natural focusing reflex is linked to convergence, this extra effort inadvertently causes the eyes to turn inward.
A family history of strabismus or amblyopia suggests a genetic predisposition. Esotropia can also be a sign of a broader systemic condition, such as neurological disorders, stroke, or nerve damage from diabetes, which directly affect the nerves or muscles responsible for eye movement.
Corrective Approaches
Treatment for esotropia is tailored to the specific type and cause, focusing on achieving eye alignment and restoring functional binocular vision.
Optical Correction
For accommodative esotropia, the primary non-surgical approach involves corrective lenses. Spectacles provide the full hyperopic correction, eliminating the need for excessive focusing effort and allowing the eyes to straighten naturally. If the eye turn is worse at near viewing distances, bifocal lenses may be prescribed to reduce focusing demand for close-up tasks. Prism lenses offer an optical solution by bending the light entering the eye, which helps to shift the image onto the fovea of the deviated eye, managing double vision and reducing strain. These prisms can be temporary or permanent additions to the corrective spectacles.
Vision Therapy
Vision therapy includes structured eye exercises used to improve eye coordination and communication between the eyes and the brain. If amblyopia (“lazy eye”) has developed, occlusion therapy, often involving patching the stronger eye, forces the weaker eye to work harder and improve its vision.
Surgical Intervention
Surgery is generally reserved for infantile esotropia or when optical and therapeutic methods fail to fully align the eyes. The procedure involves adjusting the length or position of the extraocular muscles, typically by weakening the muscles that pull the eye inward. While surgery corrects physical alignment, vision therapy or corrective lenses often follow to optimize visual function and ensure the brain accepts the eyes’ new, straighter position.