Crossed Eyes or Strabismus is an eye misalignment most commonly found in children. It is better if it’s treated in childhood so that they don’t face any issues when they grow up. Let’s understand this condition in more detail and understand how you can help your child.

What is Strabismus?

Crossed eyes are a condition where the eyes don’t line up with one another and point in different directions. While one eye may look ahead, the other may turn up, down, in or out. This misalignment may not be restricted to one eye only, it can shift from one eye to another. Strabismus not only affects the eye’s alignments but can also affect vision, as both eyes do not point in the same direction.

Why does it Occur?

Our eyes are controlled by six muscles, which control and move how they move. The brain gives signals to these muscles and directs their movement. Normally, the eyes work together to make them point in the same direction. However, sometimes issues may develop with eye movement control which leads to eyes being misaligned or they may turn in different directions. This turning may occur all the time or only under certain circumstances such as when a person is ill. The same eye may not turn all the time, different eyes may turn at different times.

Correct eye alignment is important for a variety of reasons – for good depth perception, to avoid seeing double and to lose proper vision in the turned eye. Due to the misaligned eye, the brain receives two different images which can create double vision, and in turn, confusion. However, over time, the brain learns to ignore the image from the turned eye. Untreated strabismus can lead to permanent reduction in the eye’s vision, which can ultimately develop into amblyopia or lazy eye.

Sometimes while the eyes of some babies appear to be misaligned, they may be aiming at the same object. This condition is called pseudostrabismus or false strabismus. Sometimes someone may appear to have a crossed eye due to a wide bridge of the nose or an extra skin that covers the inner corner of the eyes. These issues usually go away as the baby grows up and the face becomes larger.

Strabismus in children is associated with certain disorders as well such as:

Types of Strabismus

Strabismus can be of various types, the most common ones are:

• Accommodative esotropia: This is most common where farsightedness hasn’t been corrected or there’s a family history of crossed eyes. As the ability to focus is linked to where the eyes point, the extra effort required to focus on distant objects may cause the eyes to turn in.
• Intermittent exotropia: This is a type of strabismus where one concentrates on a target while the other points outward. Often the eye alternates between looking straight and turning outward.
• Infantile esotropia: In this kind of strabismus infants who a significant inwardly turned eye before they are six months old. It may start as an inward crossing once in a while but it can become constant over time. It can occur when your little one looks far away and up close. Glasses cannot correct this kind of crossing as this kind of strabismus doesn’t include significant farsightedness. Surgery on the muscles of one or both eyes is one of the main treatments for this kind of crossed eyes.

Strabismus is also categorised based on which way the eye points, whether only one eye is affected or both.

Based on this, strabismus is classified into:

Both exotropia and esotropia are kinds of horizontal strabismus.

Both hypertropia and hypotropia are forms of vertical strabismus.

• Intermittent strabismus or transient strabismus based on whether it happens constantly or sometimes.
• Unilateral strabismus is based on whether it happens in the same eye.
• Alternating strabismus is based on whether it happens in only one eye or even in the other eye sometimes.

Strabismus is also classified based on the nerves that are not working correctly such as abducens palsy, oblique palsy or oculomotor palsy.

When do these symptoms appear?

Symptoms of strabismus usually appear in infants and young children, by the time they turn three. However, sometimes newborns can be born with crossed eyes. Usually, an infant will be able to focus on small nearby objects by the age of three to four months. By the age of 6 months, they should be able to focus on objects near and far.

The sudden appearance of strabismus in older children or adults can indicate a more serious neurologic disorder. They often experience double vision. If your older child suddenly develops crossed eyes or sees double vision, take them to the doctor right away.

Risk Factors

So, what are the risk factors associated with crossed eyes?

• Poor vision in one eye
• Uncorrected refractive errors
• Down syndrome
• Cerebral palsy
• Brain tumour
• Hydrocephalus
• Head injury
• Neurological disorders

Complications of Crossed Eyes

Strabismus gets worse the longer it is left untreated. Untreated strabismus can lead to:

• Amblyopia or lazy eye
• Eye strain
• Blurry vision
• Fatigue
• Double vision
• Headache
• Poor three-dimensional vision

All these can affect a child’s performance at school and interfere with the child’s daily life. It can also lead to low self-esteem from how the child’s eyes look. Untreated strabismus can also lead to brain tumours in severe cases.

Diagnosis of Strabismus

Crossed eyes are primarily diagnosed through a comprehensive eye examination. However, your optometrist may conduct further diagnostic tests to understand how the eyes focus and move such as:

• History of the patient: To begin with, your optometrist will ask you about your child’s symptoms, general health condition, environmental factors and medications that your child is taking.
• Visual sharpness: Your optometrist will measure your child’s visual sharpness to understand how much the vision is affected. If your child can read, they will be asked to read some text to establish the extent of the problem. In case your child is too young to do any of the above, your optometrist may try other methods.
• Refraction: Your optometrist will next conduct refraction to establish the lens power that they require to correct the refractive error. This is done using an instrument called a phoropter.
• Focusing and alignment testing: Next, your optometrist will aim to assess how much your child’s eyes can focus and move. For clear vision, both eyes must effectively move, change focus and work in tandem. These tests aim to establish how much your child’s eye can focus and work together.

The final aim of all these tests is to understand the external and internal structures of your eyes and rule out other diseases that may be contributing to strabismus. Your optometrist will also try to establish how your child’s eyes respond under normal seeing conditions. If your child is too young and unable to respond to respond to the doctor, your doctor may use eye drops to prevent the eyes from temporarily changing focus.

This information is used by your optometrist to determine if your child has strabismus and the extent of the disease.

Factors considered during diagnosis

Your optometrist might consider certain factors while conducting tests on your child for diagnosing strabismus such as:

• Has it been diagnosed within the first six months of a child’s life?
• Did the problem develop over time or appear suddenly?
• What’s the degree of turning? Is it large, moderate or small?
• Does it affect the same eyes or switch between the two eyes?
• Is there a family history of strabismus?
• Is it always present or only sometimes?

Treatment of Strabismus

Let’s talk about treatment now. When it comes to strabismus, a variety of treatment options are available. Treatment is decided based on the type and seriousness of the issue. The treatment options include:

• Eyeglasses or contact lenses: The first line of treatment often is eyeglasses or contact lenses. Corrective lenses are used to keep your eyes straight so that they require you to focus less.
• Prism lenses: These are special lenses that blend light entering your child’s eye. They can provide relief to the eye from double vision.
• Eye exercises: Your optometrist may suggest eye exercises for treating certain kinds of strabismus including a type of exotropia known as convergence insufficiency.
• Patching: If your child has strabismus along with amblyopia, then your doctor may patch an eye to improve vision and improve the control of misalignment.
• Medications: In case an overactive eye muscle is diagnosed, medications such as ointments, eye drops or injections are commonly used to weaken the muscle. Medications are sometimes suggested instead of surgery based on the situation.
• Strabismus Surgery: Your doctor may suggest surgery to change the position or length of the eye muscle so that your child’s eyes are aligned correctly. This surgery is performed under general anaesthesia.

Usually, treatment of strabismus takes multiple visits and follow-up appointments before you can see improvement.

Can Strabismus be Prevented?

Unfortunately no, it is not preventable and neither happens due to anyone’s fault. However, early detection makes a world of change to the prognosis, hence, it is essential to meet an optometrist as soon as you detect something is wrong with your child’s eyes. Following the appointment schedule is also highly recommended to obtain the best results.

Sources:

• https://medlineplus.gov/ency/article
• https://my.clevelandclinic.org/health/diseases/strabismus-eye-misalignment
• https://www.aoa.org/healthy-eyes/eye-and-vision-conditions/strabismus
• https://www.aao.org/eye-health/diseases/what-is-strabismus
• https://www.hopkinsmedicine.org/health/conditions-and-diseases/strabismus