Esotropia is a type of eye misalignment where one or both eyes turn inward, toward the nose. It’s the most common form of strabismus (crossed eyes) and can appear at any age, from the first few months of life through adulthood. Some cases are constant, while others come and go. The cause, severity, and treatment all depend on which type of esotropia a person has.
Types of Esotropia
Esotropia is broadly split into two categories. In concomitant esotropia, the degree of inward turning stays roughly the same no matter which direction the eyes look. In incomitant esotropia, the misalignment changes depending on gaze direction, often because a specific eye muscle or nerve is affected. Most childhood cases are concomitant, and they fall into a few distinct subtypes.
Infantile Esotropia
This type appears within the first six months of life. The inward turning is typically large and constant, with a deviation of more than 30 degrees. Babies with infantile esotropia often alternate which eye turns in, and they may cross-fixate, using the left eye to look right and the right eye to look left. There’s usually no significant farsightedness driving the misalignment, which distinguishes it from the accommodative type. Surgery is considered the standard treatment, since the deviation is too large for glasses or exercises to correct on their own.
Accommodative Esotropia
Accommodative esotropia typically shows up around age 2 to 3 and is driven by farsightedness. When a farsighted child focuses hard to see clearly, the extra effort triggers a reflexive inward pull of both eyes. Three factors work together: uncorrected farsightedness, the natural link between focusing and convergence, and a weak ability to push the eyes back apart. In most cases, properly prescribed glasses reduce or eliminate the crossing by removing the need to over-focus. Children with this type usually have moderate to high farsightedness, in the range of 2 to 6 diopters.
A related subtype involves a high ratio between focusing effort and convergence response (called the AC/A ratio). In these children, farsightedness may be minimal, but any focusing effort produces an exaggerated inward turn. The crossing tends to be much worse at near distances than far, so reading and close-up tasks are especially problematic. Bifocal lenses often help by reducing the focusing demand at near.
Sensory and Consecutive Esotropia
When one eye loses significant vision from another condition, such as a cataract or eye injury, the brain may stop using that eye for alignment. The weaker eye drifts inward, resulting in sensory esotropia. Consecutive esotropia is different: it happens after surgery for the opposite problem, exotropia (outward-turning eyes), when the correction overshoots.
Esotropia in Adults
Adults can develop esotropia suddenly, and the cause list is longer than in children. Sixth nerve palsy, where the nerve controlling the muscle that pulls the eye outward stops working properly, is one of the more common triggers. Thyroid eye disease, myasthenia gravis, and age-related weakening of the eye muscles can also be responsible.
In some cases, sudden-onset esotropia in an adult signals a neurological problem. Brain tumors affecting the cerebellum, brainstem, or pituitary region, Arnold-Chiari malformations, multiple sclerosis, and elevated pressure inside the skull have all been linked to acute esotropia. This is why new-onset double vision with eye crossing in an adult typically prompts brain imaging to rule out serious causes.
Symptoms and What It Looks Like
The most obvious sign is a visible inward turn of one or both eyes. In intermittent esotropia, the crossing comes and goes, sometimes triggered by fatigue, illness, or focusing at a particular distance. Constant esotropia is present all the time.
Adults and older children with sudden esotropia almost always notice double vision, because their brains have already learned to use both eyes together. Young children rarely complain of double vision. Instead, the brain suppresses the image from the turned eye, which avoids confusion but creates a different problem: the turned eye may never develop strong vision.
Depth perception suffers when the eyes aren’t aligned. Binocular vision, the ability to combine slightly different images from each eye into a single three-dimensional picture, requires both eyes pointing at the same target. People with untreated esotropia often struggle with tasks that depend on depth judgment, like catching a ball or parallel parking.
How It’s Diagnosed
Diagnosis starts with a cover test, one of the simplest and most reliable exams in eye care. The examiner covers one eye while watching the other. If the uncovered eye shifts outward to pick up fixation, it was turned inward, confirming esotropia. Alternating the cover back and forth between eyes reveals the full extent of misalignment.
To measure the exact degree of turning, the examiner places a prism in front of one eye during the cover test and adjusts the prism strength until no movement is seen when the cover switches. This is the prism and alternate cover test. For very young children who can’t cooperate with this method, clinicians use a light-based technique, positioning a prism in front of the fixating eye until the light reflections on both corneas look symmetrical.
A full evaluation also includes checking for farsightedness (often using eye drops that relax the focusing muscles to get a more accurate reading), assessing eye movement in all directions, and evaluating binocular vision. These details determine which subtype of esotropia is present and guide treatment.
Pseudoesotropia: When It Only Looks Crossed
Many young children are referred for evaluation only to find out their eyes are perfectly aligned. The culprit is usually prominent epicanthal folds, the skin folds at the inner corners of the eyes common in babies and toddlers with flat nasal bridges. These folds cover the white of the eye near the nose, creating the illusion that the eyes are crossing. The effect is especially noticeable when a child looks to the side, as the eye appears to disappear under the fold. A simple cover test confirms normal alignment, and no treatment is needed. As the nasal bridge grows, the appearance resolves on its own.
Treatment Options
Treatment depends entirely on the type and severity. For accommodative esotropia, glasses are the first and often only intervention needed. Full correction of the farsightedness removes the excessive focusing effort that drives the convergence. Some children wear bifocals to manage a high AC/A ratio. When glasses reduce the crossing but don’t eliminate it, the remaining misalignment is called partially accommodative esotropia, and surgery may be considered for the residual deviation.
For infantile esotropia and other large, non-accommodative types, surgery on the eye muscles is the primary treatment. The most common approach is bilateral medial rectus recession, where the muscles that pull both eyes inward are loosened by moving their attachment points slightly back on the eyeball. In other cases, one eye gets both a recession of the inner muscle and a strengthening of the outer muscle. A large UK study of 70 patients with various types of esotropia found that 50% achieved successful alignment at six weeks after surgery, with an overcorrection rate of only 1.4%. Some patients need more than one operation to reach stable alignment.
Botulinum toxin injections offer a non-surgical alternative, particularly for infantile esotropia. The toxin temporarily paralyzes the overactive inner eye muscle, letting the outer muscle pull the eye back into alignment. When the paralysis wears off after several months, the alignment may hold. This approach avoids surgery but sometimes requires repeat injections.
For certain types of acquired esotropia in adults, especially smaller deviations, prism lenses and vision therapy can be effective. Prisms are incorporated into glasses to bend light so that images land on corresponding spots in both eyes, eliminating double vision without changing eye position. Vision therapy exercises then work to strengthen the ability to diverge (push the eyes apart), and over time, the prisms can sometimes be reduced or removed. One clinical review found that about 79% of patients with non-accommodative, non-neurological acquired esotropia could be managed non-surgically through prisms and vision therapy.
What Happens Without Treatment
In children, the greatest risk of untreated esotropia is amblyopia, sometimes called “lazy eye.” When one eye is consistently turned, the brain learns to ignore its input to avoid double vision. Over time, the neural pathways serving that eye weaken, and vision in that eye deteriorates. If this isn’t addressed during the first decade of life, the vision loss becomes permanent. Even if the eye is later straightened surgically, the brain may never fully recover its ability to process images from that eye.
Amblyopia treatment typically involves forcing the brain to use the weaker eye, usually by patching the stronger eye or using blurring drops in it. The earlier this starts, the better the outcome. Beyond vision loss, untreated esotropia also eliminates the possibility of developing normal binocular vision and depth perception, which has practical consequences for activities ranging from sports to driving.