Strabismus (squint/cross eyed)

What exactly is strabismus (squint/cross eyed)?

Strabismus is when someone’s eyes fail to work in synchronisation, and when eyes appear to be set in different directions. With strabismus, one eye looks straight ahead, while the other one looks either more outwardly or inwardly. Strabismus is sometimes known as squint eye.¹

When the eye is misaligned inwardly, it is known as esotropia, whereas one eye directed more outwardly is known as exotropia. Two other types of strabismus are hypertropia (where one eye looks upward), and hypotropia (where it looks downward).²

Another thing to bear in mind is that the eye’s placement and misdirection can be constant, or it can be intermittent. This means a person’s eye can alternate between being aligned and misaligned, or it may be misaligned permanently.

As strabismus is a condition that mainly affects children, those children who are affected by it may be at a greater risk of developing double vision at an early age.³,⁴ This is mainly because the brain has not yet developed to the maturity it needs to send and receive visual signals properly. This then may lead to another eye condition known as amblyopia or lazy eye, as well as strabismus.⁵

What causes strabismus?

When the six muscles present in each eye (which are all responsible for controlling its movement) suffer from an imbalance, your eye movement can be compromised, leading to uneven and misaligned eyes. The muscles must work together as a team, but when there is an imbalance, it becomes hard for them to work together, resulting in misalignment.⁶

When this happens, often one eye is less fluent in movement than the other, and may move more freely, causing it to lose focus and resulting in strabismus. The only way your eyes can focus on an object clearly is when both eyes are aligned and coordinated, along with the support of brain signals. This is crucial since the brain is the primary organ that controls eye movement.⁷

In a normal scenario, both eyes work well, because they receive accurate signals from your brain. These signals allow both eyes to view the same image at the same point – which is then processed by your brain, combining both these images into a single three-dimensional image.⁸

However, when one or both eyes are out of alignment, as with strabismus, these images are not correctly perceived by the brain. This causes the brain to ignore the image signal from the misaligned eye, instead relying on the dominant one for clear imagery. As a result, the child may lose the ability to perceive images with depth, and instead view images as blurry or duplicate.⁹

Although adult strabismus exists, strabismus is a condition that mainly affects children at a young age.¹⁰

Other causes for strabismus can be eye injuries and premature cataracts in children, which can cause a muscular imbalance in the eye if not treated. Children with strabismus are more likely to squint their dominant, better-seeing eye to see images clearly, especially when out in bright daylight.¹¹

Strabismus symptoms

Pseudostrabismus

Children and adults with strabismus can have a false cross-eyed appearance, when in fact, they have pseudostrabismus rather than genuine strabismus. Pseudostrabismus is when an adult or young child has a flat, wide nose, together with a fold in the skin of the inner eyelid. An additional characteristic of pseudostrabismus can be double vision. Physically, the fold in the skin of the inner eyelid can improve as the child grows; however, genuine strabismus does not improve with age.¹²

Why is my child or newborn cross-eyed?

Here are the most common types of strabismus causing a squint in babies and children:¹³,¹⁴

Esotropia: This kind of strabismus is when the eyes are turned inwards, and tends to be common in infants. Children with esotropia may struggle to make their eyes work together and may need vision therapy to get both eyes to work as a team.
Accommodative esotropia: In this type of strabismus, the child's eyes turn inwards upon focusing on a single object to see it clearly. This can also happen in the case of focusing on an object in the distance.
Exotropia: Exotropia is the opposite of esotropia and involves the turning outwards of one or both eyes. It is also known as divergent strabismus or divergent squint. With this type of strabismus, the child may struggle to view and focus on objects at a distance, and may need to squint one eye to see objects clearly (particularly in broad daylight).

Medically reviewed by Dan McGhee on September 29, 2022

Strabismus (squint/cross eyed)

Strabismus symptoms

Sources

Related topics: