Childhood Strabismus: Crossed Eyes Symptoms, Causes & Treatment

What Is Strabismus in Children?

Strabismus is a condition where the eyes are misaligned and point in different directions. One eye may look straight ahead while the other turns inward (esotropia), outward (exotropia), upward, or downward. This misalignment prevents both eyes from focusing on the same point, which can lead to double vision and loss of depth perception.

Strabismus, commonly known as crossed eyes, squint, or wall eyes, is one of the most common eye conditions affecting children. The condition occurs when the muscles that control eye movement do not work together properly, causing the eyes to point in different directions. While one eye looks directly at an object, the other eye may turn in a different direction, creating a visible misalignment that can be constant or intermittent.

The impact of strabismus extends beyond the cosmetic appearance. When the eyes are not properly aligned, each eye sends a different image to the brain. In young children, the brain typically responds by ignoring or suppressing the image from the misaligned eye to avoid double vision. While this adaptation prevents the uncomfortable sensation of seeing double, it comes at a significant cost: the suppressed eye does not develop normal visual acuity, a condition known as amblyopia or "lazy eye."

Understanding the distinction between different types of strabismus is essential for proper treatment. Esotropia (inward turning of the eye) is the most common type in infants and young children, while exotropia (outward turning) tends to develop later in childhood. The direction of misalignment, whether it's constant or intermittent, and whether it affects one eye consistently or alternates between eyes all influence the treatment approach and prognosis.

How the Brain Processes Misaligned Eyes

In normal vision, both eyes focus on the same object simultaneously. The brain receives two slightly different images (one from each eye) and combines them into a single three-dimensional image. This process, called binocular vision, provides depth perception and the ability to judge distances accurately. The slight difference between the images from each eye—called binocular disparity—is what allows us to perceive depth.

When strabismus causes the eyes to point in different directions, the brain receives two completely different images rather than two similar views of the same scene. In adults, this typically causes double vision (diplopia), which can be extremely disorienting and uncomfortable. However, children's brains are remarkably adaptable. To cope with this visual conflict, a child's developing brain often simply "turns off" or suppresses the input from the misaligned eye.

This neural suppression is a double-edged sword. While it prevents double vision and allows the child to function normally day-to-day, it also means the visual pathways from the suppressed eye are not being used and developed. Vision is a learned skill that requires proper stimulation during critical developmental periods. Without this stimulation, the visual acuity in the suppressed eye fails to develop normally, resulting in amblyopia.

Types of Strabismus

Strabismus can be classified by the direction of eye deviation, its consistency, and other characteristics. Understanding these classifications helps healthcare providers determine the most appropriate treatment approach.

What Causes Strabismus in Children?

Strabismus can be caused by refractive errors (such as farsightedness), hereditary factors, eye muscle problems, nerve dysfunction, or underlying medical conditions. In many cases, the exact cause cannot be identified. Sudden onset of strabismus may indicate a serious neurological condition requiring immediate evaluation.

The development of strabismus in children is complex and often multifactorial. While the visible result is misaligned eyes, the underlying causes involve intricate interactions between the eye muscles, the nerves that control them, and the brain's visual processing centers. Understanding these causes is essential for determining the most effective treatment approach.

The six extraocular muscles that control each eye's movement must work in precise coordination. These muscles are controlled by three cranial nerves (the oculomotor, trochlear, and abducens nerves), which receive instructions from multiple brain regions. A problem at any point in this complex system—from the muscles themselves to the highest brain centers—can result in strabismus.

Refractive Errors

Refractive errors, particularly farsightedness (hyperopia), are among the most common causes of childhood strabismus. When a child is significantly farsighted, they must exert extra effort to focus on near objects. This focusing effort (accommodation) is neurologically linked to the convergence of the eyes (turning inward). Excessive accommodation can therefore cause excessive convergence, resulting in esotropia—a condition called accommodative esotropia.

Accommodative esotropia typically appears between ages 2 and 3, when children begin doing more close-up activities like looking at books and toys. The good news is that this type of strabismus often responds well to treatment with glasses. By correcting the farsightedness with appropriate prescription lenses, the child no longer needs to accommodate excessively, and the eye alignment often improves dramatically or even normalizes completely.

Astigmatism and significant differences in prescription between the two eyes (anisometropia) can also contribute to strabismus development by creating unequal visual input that the brain struggles to integrate.

Hereditary Factors

Strabismus has a strong genetic component. Children with a parent or sibling who has strabismus are at significantly higher risk of developing the condition themselves. Studies suggest that approximately 30% of children with strabismus have a family history of the condition. The inheritance pattern is complex and likely involves multiple genes rather than a single gene.

If you have strabismus or it runs in your family, it's important to have your children's eyes examined early and regularly. Early detection allows for prompt treatment during the critical period when intervention is most effective.

Eye Diseases and Injuries

Any condition that affects one eye's ability to see clearly can lead to strabismus. When one eye has significantly better vision than the other, the brain tends to favor the better-seeing eye, and the poorer-seeing eye may drift out of alignment. Conditions that can cause this include:

• Congenital cataracts: Cloudiness of the eye's natural lens present at birth
• Retinal problems: Conditions affecting the light-sensitive tissue at the back of the eye
• Optic nerve abnormalities: Problems with the nerve connecting the eye to the brain
• Eye injuries: Trauma affecting the eye or surrounding structures

Neurological Conditions

Because eye muscle control involves complex neural pathways, various neurological conditions can cause strabismus. This is particularly important to recognize because sudden onset of strabismus in a child who previously had normal eye alignment may be a warning sign of a serious neurological problem.

Other neurological causes of strabismus include cerebral palsy, hydrocephalus, and conditions that affect the cranial nerves controlling eye movement. Certain infections, such as Lyme disease (borreliosis), can also affect the nerves and muscles controlling eye movement.

Normal Newborn Eye Crossing

It is completely normal and common for newborn babies to have intermittent eye misalignment during their first few months of life. The visual system is not fully developed at birth, and the coordination between the eyes improves as the baby grows. The eye muscles and the neural pathways controlling them are still maturing, so occasional crossing or wandering of the eyes is expected.

By approximately 3-4 months of age, most babies can consistently coordinate their eye movements and maintain proper alignment. If your baby continues to show eye misalignment after this age, or if the strabismus is constant rather than intermittent from birth, you should consult a pediatric eye specialist for evaluation.

What Are the Signs and Symptoms of Strabismus?

Signs of strabismus include visible eye misalignment, head tilting or turning, closing one eye in bright light, difficulty with depth perception, eye strain, and headaches. In hidden strabismus, symptoms may only appear when the child is tired or ill. Parents often first notice the condition in photographs where flash reveals unequal eye positioning.

Recognizing the signs of strabismus early is crucial for timely intervention. While obvious eye misalignment is the most visible sign, there are many other indicators that parents and caregivers should watch for. Some children develop compensatory behaviors to cope with their visual problems, which can be clues to underlying strabismus.

Visible Eye Misalignment

The most apparent sign of strabismus is when the eyes do not appear to look in the same direction. One eye may turn inward toward the nose, outward toward the ear, or vertically up or down while the other eye looks straight ahead. This misalignment may be:

• Constant: Present all the time
• Intermittent: Coming and going, often worse when tired, ill, or during certain activities
• Unilateral: Always affecting the same eye
• Alternating: Switching between eyes

It's worth noting that some apparent eye misalignment is actually an illusion caused by facial features. Wide nasal bridges or extra skin folds near the nose can make a child's eyes appear crossed when they are actually straight—a condition called pseudostrabismus. A proper eye examination can distinguish between true strabismus and pseudostrabismus.

Head Positioning

Children with strabismus often adopt abnormal head positions to compensate for their misaligned eyes. By tilting or turning their head, they may be able to achieve better eye alignment or avoid double vision. If your child consistently:

• Tilts their head to one side
• Turns their face to the left or right
• Raises or lowers their chin

This could indicate strabismus or another eye muscle problem. These head positions become habitual because they help the child see more comfortably, even if the child is not consciously aware of why they do it.

Behavioral Signs

Children with strabismus may exhibit various behaviors that reflect their visual difficulties:

• Closing or covering one eye: Especially in bright sunlight or when trying to focus on something
• Squinting: Attempting to improve focus or reduce double vision
• Rubbing eyes frequently: Due to eye strain or fatigue
• Difficulty with activities requiring depth perception: Such as catching balls, going down stairs, or pouring liquids
• Avoiding close work: Reading or drawing may be uncomfortable

Hidden Strabismus (Latent Strabismus)

Some children have hidden or latent strabismus (also called phoria), where the eye misalignment is not visible under normal conditions. The child can maintain proper eye alignment through muscular effort, but this constant effort can lead to symptoms, particularly when the child is tired, sick, or has been doing extensive near work.

Symptoms of hidden strabismus include:

• Eye fatigue: Eyes feel tired, especially after reading or screen time
• Headaches: Particularly after visual tasks
• Intermittent double vision: When the child can no longer maintain alignment
• Difficulty concentrating: Visual strain makes sustained attention difficult

Hidden strabismus typically becomes more apparent when the child is fatigued or unwell because they lack the energy to maintain the muscular effort needed to keep the eyes aligned. This is why parents may notice their child's eyes drifting apart when they're tired.

How Is Strabismus Diagnosed?

Strabismus is diagnosed through comprehensive eye examinations including visual acuity testing, cover tests to detect and measure misalignment, assessment of eye movement and coordination, and refraction testing to check for glasses needs. Examinations are performed by orthoptists (specialized eye care professionals) and ophthalmologists using child-friendly methods.

Early diagnosis of strabismus is essential for effective treatment. Children should have their eyes examined at regular intervals during childhood, and any concerns about eye alignment should prompt an evaluation by an eye care professional. The diagnostic process involves several specialized tests designed to detect both obvious and subtle forms of strabismus.

Visual Acuity Testing

Measuring how well each eye sees is a fundamental part of strabismus evaluation. This helps determine whether amblyopia has developed and guides treatment decisions. For children too young to read letters, age-appropriate tests are used:

• Picture charts: Using recognizable images instead of letters
• Symbol matching: The child points to a matching symbol on a handheld card
• Preferential looking tests: For infants, observing which direction they look when shown patterns

Each eye is tested separately by covering the other eye. This is important because if both eyes are tested together, a child with strabismus may be using only their better eye without anyone realizing the other eye sees poorly.

Cover Tests

The cover test is the key examination for detecting and measuring strabismus. It works by breaking the fusion between the two eyes and observing any movement that occurs. The examination is painless and typically proceeds as follows:

The examiner has the child focus on a target (a toy or light) while covering and uncovering each eye in turn. They watch for any movement of the eyes when one is covered or uncovered. In strabismus, when the straight eye is covered, the misaligned eye must move to take up fixation on the target. Similarly, when the cover is removed, there may be movement as the eyes adjust.

This test can detect both manifest strabismus (where misalignment is visible) and latent strabismus (where misalignment is hidden until one eye is covered). The test is performed at both distance and near to assess alignment at different viewing distances.

Eye Movement Assessment

The examiner tests how well the eyes can move in all directions—up, down, left, right, and diagonally. The child is asked to follow a moving target (often a toy or the examiner's finger) while keeping their head still. This assessment reveals:

• Whether any eye muscles are weak or paralyzed
• How well the eyes track together as a team
• Whether the strabismus varies in different directions of gaze

Refraction Testing

Determining whether the child needs glasses is crucial because refractive errors are a common cause of strabismus. For children, eye drops are often used to temporarily relax the focusing muscles (cycloplegic refraction). This is important because children can compensate for refractive errors through accommodation, which can mask the true prescription.

The drops dilate the pupils and may cause temporary light sensitivity and blurred near vision for several hours. Parents should be prepared to protect their child's eyes from bright light after the examination and understand that reading vision may be blurred until the drops wear off (typically 3-6 hours, sometimes longer).

Assessment of Binocular Vision

The examiner also assesses whether the child can use both eyes together effectively. Tests measure:

• Stereopsis: The ability to perceive depth using both eyes
• Fusion: The ability to combine images from both eyes into one
• Suppression: Whether the brain is ignoring input from one eye

These assessments help predict how well treatment will restore normal binocular vision and guide decisions about the timing and type of intervention.

How Is Childhood Strabismus Treated?

Strabismus treatment depends on the type and cause but may include corrective glasses to address refractive errors, patching or atropine drops to treat amblyopia, vision therapy exercises, and surgery to adjust eye muscle tension. Treatment often combines multiple approaches. Early intervention produces the best outcomes for vision development.

The goals of strabismus treatment are threefold: to achieve the best possible vision in each eye, to align the eyes so they work together, and to develop or restore binocular vision with depth perception. Treatment plans are individualized based on the type of strabismus, the child's age, the presence of amblyopia, and the underlying cause.

Glasses for Refractive Errors

When strabismus is caused by or associated with refractive errors, glasses are often the first line of treatment. For children with accommodative esotropia, glasses that correct farsightedness can dramatically improve or even eliminate the eye crossing. The glasses reduce the focusing effort needed to see clearly, which in turn reduces the excessive convergence.

Children may initially resist wearing glasses, but most adapt quickly, especially when they experience improved vision. It's important that children wear their glasses consistently for treatment to be effective. Some key points about glasses for strabismus:

• The prescription may seem stronger than expected because it must fully correct the refractive error
• Bifocals are sometimes prescribed if the child has more crossing at near than at distance
• Regular follow-up is needed as prescriptions can change as children grow
• Glasses treat only the portion of strabismus related to refractive error; additional treatment may be needed for remaining misalignment

Patching Therapy for Amblyopia

If the child has developed amblyopia (reduced vision in the misaligned eye), patching therapy is typically needed. The goal is to strengthen the weaker eye by forcing the brain to use it. This involves covering the stronger eye with an adhesive patch for a prescribed number of hours each day.

Patching works by eliminating the brain's preference for the stronger eye. When the good eye is covered, the brain must rely on the weaker eye, stimulating the development of visual pathways that had been suppressed. Key aspects of patching therapy include:

• Duration varies: From 2 to 6+ hours daily depending on severity
• Consistency is crucial: The prescribed patching schedule must be followed for treatment to work
• Activities while patching: Near-vision activities like reading, drawing, or playing with small toys enhance effectiveness
• Regular monitoring: Vision in both eyes is checked regularly to assess progress and adjust treatment
• Treatment duration: May continue for months to years until vision equalizes or reaches maximum potential

Patching can be challenging for families. Children often resist wearing the patch, and compliance can be difficult. Strategies to improve cooperation include making patching time special with favorite activities, using patches with fun designs, and involving the child in choosing their patches. Support from family, teachers, and peers can make a significant difference.

Atropine Drops as Alternative to Patching

For some children, atropine eye drops in the stronger eye can be used instead of or in addition to patching. Atropine temporarily blurs vision in the stronger eye by dilating the pupil and paralyzing focusing, which encourages use of the weaker eye. This approach may be easier for some families to implement and can be effective for mild to moderate amblyopia.

Surgery for Strabismus

When glasses and patching do not adequately align the eyes, surgery may be recommended. Strabismus surgery adjusts the tension in the eye muscles to improve alignment. The procedure involves making small incisions in the conjunctiva (the clear tissue covering the white of the eye) to access the muscles, then either:

• Weakening (recession): Moving a muscle's attachment point backward to reduce its effect
• Strengthening (resection): Removing a portion of muscle to increase its effect

Surgery may be performed on one or both eyes, depending on the type and degree of strabismus. Important points about strabismus surgery:

• Success rates: 85-95% of patients achieve improved alignment
• Multiple surgeries: Some children need more than one procedure for optimal results
• Timing: Surgery may be done at various ages; earlier is often better for certain types
• Still need glasses: Surgery corrects alignment but doesn't change refractive error
• Continued monitoring: Follow-up is needed for years after surgery

For children who wear glasses, surgery addresses only the portion of strabismus visible when wearing glasses. This means some crossing or drifting may still occur when glasses are removed, but the child should appear aligned when glasses are worn.

Vision Therapy

Vision therapy, also called orthoptic exercises, involves structured activities designed to improve eye coordination and focusing abilities. While it cannot correct significant strabismus on its own, vision therapy may be helpful for:

• Hidden (latent) strabismus causing symptoms
• Intermittent strabismus to improve control
• After surgery to optimize results
• Building binocular vision skills

A simple example of a vision therapy exercise is focusing on a finger while slowly bringing it toward the nose, training the eyes to converge. Professional vision therapy programs involve more sophisticated exercises and may use specialized equipment.

When Should You Seek Medical Care?

Seek evaluation if your child shows eye misalignment after 3-4 months of age, misaligns eyes constantly at any age, has intermittent strabismus after 6 months, or suddenly develops strabismus without previous history (urgent). Regular eye screening is recommended at birth, 4 weeks, 6 months, and at ages 4-5.

Early detection and treatment of strabismus significantly improves outcomes. Parents and caregivers play a crucial role in identifying potential problems and seeking timely evaluation. Understanding when to seek care helps ensure children receive appropriate intervention during the critical periods of visual development.

When to Contact Healthcare Providers

Contact a healthcare provider for eye evaluation if:

• Your child is older than 3-4 months and shows constant eye misalignment
• Your child is older than 6 months and shows intermittent eye misalignment
• You notice your child tilting or turning their head consistently
• Your child closes or covers one eye frequently
• Your child complains of double vision, eye strain, or frequent headaches
• You have family history of strabismus or amblyopia

Routine Eye Screening Schedule

Children should have their eyes examined at regular intervals even without obvious problems. Recommended screening times include:

• At birth: Initial examination before leaving the hospital
• 4 weeks: Check for structural problems
• 6 months: Assessment of eye alignment and visual development
• Ages 4-5: Comprehensive vision screening including visual acuity testing
• School age: Regular screening as recommended by schools and healthcare providers

Children at higher risk (family history, premature birth, developmental delays) may need more frequent examinations. If any screening reveals concerns, referral to a pediatric ophthalmologist or specialized eye clinic is appropriate.

How Does Vision Develop in Children?

Vision develops from birth through approximately age 10, with the most critical period being the first few years. During this time, the visual cortex in the brain learns to process images, and the eyes must work together to develop binocular vision. Any disruption during this period can have lasting effects on visual function.

Understanding normal vision development helps explain why early treatment of strabismus is so important. Vision is not simply a function of healthy eyes—it requires proper development of the brain's visual processing centers. This development occurs during specific "critical periods" in childhood and depends on both eyes receiving clear, aligned images.

Visual Development Timeline

At birth, a baby's vision is quite limited. Newborns can see objects only about 8-12 inches from their face and have minimal ability to focus. Over the first years of life, vision matures rapidly:

• Birth to 4 months: Eyes begin to work together; focusing ability develops; color vision emerges
• 4 to 8 months: Eye-hand coordination develops; depth perception begins
• 8 to 12 months: Crawling and walking enhance spatial awareness; eyes can track moving objects smoothly
• 1 to 2 years: Eye-hand coordination and depth perception continue refining
• 3 to 6 years: Vision approaches adult levels; fine motor skills dependent on vision mature
• 6 to 10 years: Final refinement of visual skills; critical period for treating amblyopia closes

The Critical Period for Treatment

The concept of "critical periods" in vision development is fundamental to understanding why early treatment matters. During these periods, the visual system is highly plastic—capable of change in response to experience. This plasticity allows for normal development when conditions are favorable, but also makes the system vulnerable to disruption.

The most intense critical period for visual development occurs from birth to approximately age 3, with significant plasticity continuing until age 6-7. After this, the visual system becomes increasingly fixed, and treatment for amblyopia becomes less effective (though not impossible—recent research shows some benefit from treatment even in older children and teenagers).

This is why early detection and treatment of strabismus is emphasized. If strabismus leads to amblyopia during the critical period and is not treated, the vision loss can become permanent. Conversely, treatment during the critical period can often fully restore normal vision.

How Binocular Vision Works

Normal binocular vision requires both eyes to be aligned and to send similar images to the brain. The brain then combines these slightly different viewpoints into a single three-dimensional perception of the world. This fusion provides important visual abilities:

• Stereopsis (depth perception): The ability to judge distances and perceive 3D space
• Enhanced visual acuity: Two eyes together see better than one eye alone
• Wider field of view: Overlapping visual fields provide broader peripheral awareness
• Backup system: If one eye is injured or occluded, the other can still function

Strabismus disrupts this coordinated system. The misaligned eyes send conflicting information to the brain, which responds by suppressing input from one eye. This adaptive response prevents double vision but at the cost of losing binocular function and potentially causing amblyopia in the suppressed eye.