Strabismus: Causes, Symptoms, Types, and Treatment

What Is Strabismus?

Strabismus is a condition in which both eyes do not point in the same direction at the same time. When you have strabismus, one eye may look straight ahead while the other turns inward, outward, upward, or downward. This misalignment happens because the muscles controlling eye movement do not work together as they should.

You may have heard strabismus referred to as crossed eyes or wandering eye. It is more common in children, but adults can develop it too. Regardless of when it appears, it is a treatable condition, and early attention makes a significant difference.

What Is Squint Eye? Is It the Same as Strabismus?

Yes, squint eye is simply another name for strabismus. In everyday language across India, people commonly use the term "squint" to describe the visible misalignment of the eyes. Medically, both terms refer to the same condition, and they are used interchangeably.

How Do Eyes Normally Stay Aligned?

Each eye is controlled by six muscles. These muscles work in coordination to move both eyes in the same direction at the same time. Your brain manages this coordination continuously, ensuring that both eyes focus on the same point together. This teamwork allows you to see a single, clear, three-dimensional image and judge distances accurately, which is known as depth perception.

When this coordination breaks down, the eyes fall out of alignment. The brain then receives two different images from each eye instead of one unified image. In children, the brain often responds by suppressing the image from the misaligned eye, which can lead to weakened vision in that eye over time. In adults, the brain cannot easily suppress the second image, so double vision is a common experience.

Types of Strabismus

Strabismus is classified based on the direction in which the misaligned eye turns:

• Esotropia: The eye turns inward. This is the most common type in children, sometimes called "crossed eyes."
• Exotropia: The eye turns outward, sometimes called "wall eye."
• Hypertropia: The eye turns upward.
• Hypotropia: The eye turns downward.

Strabismus can also be described as:

• Constant: The misalignment is present all the time.
• Intermittent: The eye only turns occasionally, sometimes when the person is tired or unwell.
• Unilateral: Only one eye is always affected.
• Alternating: The misalignment switches between the left and right eye.

Some specific subtypes worth knowing include accommodative esotropia, which occurs when uncorrected farsightedness causes the eyes to cross inward as they strain to focus, and infantile esotropia, which appears in babies before the age of six months.

Causes of Strabismus

Muscle Imbalance and Nerve Problems

The most common underlying cause of strabismus is a problem with the neuromuscular control of eye movement. This means the brain is unable to send the right signals to coordinate the eye muscles properly. In some cases, the problem lies in the muscles themselves, which may be too weak or too stiff to allow both eyes to align.

Strabismus in Children (Congenital Causes)

In children, strabismus often appears before the age of three. Around 30% of children with strabismus have a family history of the condition, which points to a hereditary component. Certain developmental conditions also raise the risk, including cerebral palsy, Down syndrome, and hydrocephalus. Premature birth and low birth weight are additional risk factors in infants.

Strabismus in Adults

Adults can develop strabismus for the first time later in life, or they may have a childhood condition that recurs or worsens. In adults, stroke is the leading cause of new-onset strabismus. Other causes include head injuries, brain tumours, thyroid eye disease (also known as Graves' disease), diabetes, and myasthenia gravis.

Vision Problems (Refractive Errors)

Uncorrected farsightedness (hyperopia) is a well-established trigger for strabismus, particularly in children. When the eyes have to work harder than usual to focus on objects, they may turn inward to compensate. Correcting the refractive error with glasses often helps reduce or resolve this type of strabismus.

Brain and Neurological Conditions

Because the brain controls the coordination of eye muscles, any condition that affects the brain or nervous system can contribute to strabismus. This includes neurological conditions, traumatic brain injuries, and problems with the cranial nerves that control eye movement. In such cases, treating the underlying neurological condition is an important part of the overall management plan.

Symptoms of Strabismus

The symptoms of strabismus can vary depending on your age and the type of misalignment involved. Common signs include:

• Visibly misaligned eyes, with one eye pointing in a different direction
• Double vision (seeing two images of the same object)
• Blurry vision
• Loss of depth perception or difficulty judging distances
• Closing or covering one eye to see more clearly
• Tilting or turning the head to focus better
• Eye strain and fatigue
• Headaches
• Difficulty reading

In young babies, it is normal for the eyes to wander briefly in the first few months of life. However, by three to four months of age, the eyes should begin to align consistently. If you notice persistent misalignment in your infant or young child, it is worth speaking to an eye specialist promptly.

It is also important to note that a condition called pseudostrabismus can make a baby's eyes appear crossed when they are not. This happens due to extra skin folds near the inner corners of the eyes or a flat nasal bridge. As the child grows and their facial features develop, this appearance often resolves naturally.

How Is Strabismus Diagnosed?

If you suspect that you or your child has strabismus, an eye specialist will carry out a thorough examination. Here is what the diagnostic process typically involves:

• A detailed medical history, including any family history of eye conditions
• Visual acuity testing to assess how clearly each eye sees
• Alignment and cover tests to observe how the eyes move and focus
• Refraction testing to check for refractive errors such as farsightedness
• Examination of the internal structures of the eye after dilating the pupils
• Neurological evaluation if there is any suspicion of an underlying brain or nerve condition

Eye Examination and Alignment Tests

The eye doctor will observe how each eye moves and tracks objects. Cover tests, where one eye is covered at a time, help reveal the degree and type of misalignment. These tests can be performed even in very young children who are not yet able to read or respond verbally.

Vision and Refraction Testing

Refraction testing checks whether a refractive error is contributing to the strabismus. In children, special eye drops may be used to relax the focusing muscles, giving the doctor a more accurate picture of the prescription required. This is a routine part of the examination and is entirely safe.

Neurological Evaluation (If Needed)

If the strabismus appears suddenly, especially in an older child or adult, or if it is accompanied by other neurological symptoms, further investigations may be advised. This could include imaging studies such as an MRI to rule out conditions affecting the brain or cranial nerves.

Treatment Options for Strabismus

Treatment for strabismus depends on the type, severity, and underlying cause. Options include:

• Corrective glasses or contact lenses: Used when a refractive error is contributing to the misalignment. In accommodative esotropia, glasses alone may straighten the eyes significantly.
• Prism lenses: Special lenses that bend light to reduce or eliminate double vision.
• Eye patching: A patch is worn over the stronger eye to encourage the weaker eye to work harder and develop better vision. This is often used alongside other treatments.
• Eye drops: Certain medicated drops can temporarily blur the vision in the stronger eye, encouraging the weaker eye to be used more.
• Eye exercises (orthoptics or vision therapy): Targeted exercises to help both eyes work together, particularly useful for a condition called convergence insufficiency.
• Botulinum toxin (Botox) injections: Injected into an overactive eye muscle to weaken it, helping to improve alignment. The effect may be temporary or, in some cases, longer-lasting.
• Strabismus surgery: An outpatient procedure to adjust the length or position of the eye muscles so that both eyes align correctly.

Best Age to Treat Strabismus

There is no single "best" age, but early treatment generally leads to the best outcomes, especially in children. The visual system is most adaptable in the first few years of life. Treating strabismus during this period gives the best chance of restoring good vision, preventing amblyopia, and developing normal depth perception.

That said, strabismus can be treated at any age. Adults can also benefit significantly from treatment, even if the condition has been present for many years.

Strabismus Treatment in Children

In children, treatment often begins with glasses to correct any refractive error. If lazy eye (amblyopia) is present alongside the strabismus, patching the stronger eye is an important step. Surgery may be recommended if glasses alone do not achieve adequate alignment. Younger children generally respond very well to treatment, and results are often excellent when the condition is caught early.

Strabismus Treatment in Adults

Adults with strabismus have access to the same range of treatments as children. Surgery is often the most common recommendation for adults and can significantly improve eye alignment and reduce double vision. Prism glasses may also be an effective option for mild cases. The recovery from strabismus surgery is usually straightforward, and most people can return to their daily routine within a few days.

Recovery After Strabismus Surgery

Strabismus surgery is typically performed as an outpatient procedure under general anaesthesia. The surgeon makes a small cut in the tissue covering the eye and adjusts one or more of the eye muscles. Dissolvable stitches are used, so no removal is needed.

After surgery, you may notice redness, mild discomfort, and some watering of the eye for a short period. Most people recover within a few days. Follow-up appointments are important to monitor how the eye is healing and to check whether further treatment is needed. In some cases, more than one procedure may be required to achieve the desired result.

Possible Complications of Untreated Strabismus

If strabismus is left untreated, particularly in children, it can lead to a range of complications:

• Amblyopia (lazy eye): The brain begins to suppress vision from the misaligned eye, leading to permanently reduced vision in that eye.
• Loss of depth perception: Without both eyes working together, 3D vision is compromised.
• Persistent double vision: More common in adults when the brain cannot ignore the second image.
• Eye strain, fatigue, and headaches: Ongoing discomfort from the eyes working against each other.
• Impact on learning and daily activities: Blurry vision and eye strain can affect reading, school performance, and work.
• Emotional and social effects: Visible misalignment can affect self-confidence, particularly in children.

Can Strabismus Be Prevented?

Strabismus cannot always be prevented, as many cases are related to genetics, developmental factors, or underlying health conditions. However, you can take steps to support early detection and reduce the risk of complications:

• Attend all routine eye checks for your child, starting from infancy.
• Report any concerns about your child's eyes or vision to a doctor promptly.
• Keep conditions such as diabetes and thyroid disease well-managed, as these can contribute to strabismus in adults.
• Seek immediate medical attention after any head injury or stroke that affects vision.
• Never dismiss crossed eyes in a child as something they will grow out of without getting a professional opinion first.

Maintaining good overall eye health matters too. Conditions such as Vitamin A Deficiency can affect the eyes in important ways, making regular health checks and a balanced diet part of a proactive approach to eye wellness.

When to See an Eye Doctor

You should seek an eye specialist if:

• Your baby's eyes appear misaligned after three to four months of age.
• You notice that your child consistently tilts or turns their head to look at things.
• Your child or you are experiencing double vision or blurry vision.
• Strabismus appears suddenly in an older child or adult.
• There has been a recent head injury or stroke affecting vision.
• You have been diagnosed with diabetes, thyroid disease, or another condition associated with strabismus.

The sooner you seek an evaluation, the sooner appropriate treatment can begin.

Conclusion

Strabismus is a treatable condition, and with the right care at the right time, most people can achieve good outcomes. Whether you are looking after a young child whose eyes are not aligning properly, or you are an adult dealing with new-onset double vision, prompt action makes all the difference.

Taking care of your vision is a part of taking care of your overall health. At Metropolis Healthcare, we believe that staying informed and proactive is the best way to safeguard your wellbeing. From routine health screenings and full body checkups to speciality diagnostics, Metropolis offers over 4,000 tests with accurate results, quick turnaround times, and the convenience of home sample collection across 10,000 touchpoints. Book your tests easily through the website, app, call, or WhatsApp, and take one confident step towards better health today.

FAQs

Can Strabismus Be Cured?

Yes, in many cases strabismus can be effectively corrected. Treatment options such as glasses, patching, eye exercises, and surgery can significantly improve or fully resolve the misalignment. Early treatment in children tends to produce the best results. Adults can also benefit from treatment at any stage, though outcomes vary depending on the severity and duration of the condition.

Is Strabismus Serious?

Strabismus deserves prompt attention, but it is manageable with the right treatment. If left untreated, especially in children, it can lead to amblyopia, loss of depth perception, and persistent vision problems. When addressed in time, it rarely leads to serious long-term complications.

Can Strabismus Cause Permanent Vision Loss?

If strabismus is not treated in childhood, the brain may permanently suppress vision from the misaligned eye, resulting in amblyopia or "lazy eye." This can cause lasting reduced vision in that eye. This is why early detection and treatment are so important for children. In adults, permanent vision loss from strabismus alone is less common, but double vision and other visual disturbances can significantly impact quality of life.

Is Strabismus Common in Children?

Yes, strabismus is one of the more common eye conditions in children. An estimated 4% of the population is affected. It usually appears before the age of three, though it can develop at any stage of childhood.

Does Strabismus Go Away on Its Own?

In most cases, strabismus does not resolve without treatment. Some parents hope that a child will outgrow crossed eyes, but waiting without seeking medical advice can allow the condition to worsen and increase the risk of amblyopia. Always consult an eye specialist rather than adopting a "wait and see" approach.

Is Strabismus Surgery Safe?

Strabismus surgery is a well-established procedure performed routinely around the world. It is generally considered safe and effective. As with any surgery, there are some risks, but serious complications are uncommon. Your eye specialist will discuss what to expect and how to prepare so that you feel confident and reassured before proceeding.

Can Adults Develop Strabismus Suddenly?

Yes, adults can develop strabismus suddenly, and this should be taken seriously. Sudden onset strabismus in an adult, especially when accompanied by double vision, can sometimes indicate an underlying condition such as a stroke, brain tumour, head injury, or nerve problem. If this happens to you, seek medical attention promptly.

References

• Bhola R. Infantile esotropia. EyeWiki, American Academy of Ophthalmology. Updated 2022.
• American Optometric Association. Strabismus (crossed eyes). Accessed 2024.
• American Academy of Ophthalmology. Strabismus: Diagnosis and treatment. Updated 2024.
• MedlinePlus. Strabismus. U.S. National Library of Medicine. Updated 2023.
• Dagi LR, Bhola R. What is strabismus? American Academy of Ophthalmology. Published September 2024.
• Scheiman MM, Wick B. Clinical Management of Binocular Vision. 4th ed. Lippincott Williams and Wilkins; 2014.