Strabismus (Eye Misalignment)

What is strabismus?

Strabismus (sometimes called eye misalignment or ‘squint’) is a condition in which your eyes don’t line up and point in different directions. One eye may turn inwards, outwards, upwards or downwards. The misalignment may be present all the time or only happen sometimes (for example, when a child is tired or focusing on distant objects).

If you notice strabismus in children, it is important to book an eye exam as soon as possible, as it can affect visual development. If the brain begins to ignore the image from the misaligned eye, reduced vision (amblyopia or ‘lazy eye’) may develop in that eye, and depth perception may also be affected.

Early assessment and treatment can help to prevent irreversible blindness and improve vision. Sometimes, strabismus can be a sign of a more serious underlying condition.

What are the symptoms of strabismus?

The symptoms of strabismus include visibly misaligned, crossed or wandering eyes, that don’t move together. This is often accompanied by:

• Double vision
• Blurred vision
• Loss of depth perception
• Eye strain
• Tilting or turning the head
• Squinting.

What causes strabismus?

In children, causes and risk factors for strabismus include:

• The need for glasses: Particularly hyperopia (farsightedness) or a large difference in the prescription of the two eyes (anisometropia).
• Reduced vision in one eye (for example from unequal glasses prescription, cataract, droopy eyelid, or other eye conditions), which can lead to misalignment.
• A family history of strabismus.
• Developmental or neurological conditions.
• Trauma to the eye or head.

If a new or sudden squint appears in children or adults, it should be assessed immediately as it could be related to a condition affecting the brain or other serious condition.

Are there different types of strabismus?

There are different types of strabismus. The most common are:

• Esotropia: When your eye points inwards (a type of horizontal strabismus).
• Exotropia: When your eye points outwards (also horizontal strabismus).
• Hypertropia: When your eye points upwards (a type of vertical strabismus).
• Hypotropia: When your eye points downwards (a type of vertical strabismus).

Strabismus may also be described by how often it happens:

• Intermittent: When strabismus happens sometimes (may be more noticeable when tired or looking far away).
• Constant: Present all the time.And by which eye is affected:
• Unilateral: Usually happens in the same eye.
• Alternating: It happens in different eyes at different times.

Common types of strabismus in children include:

• Infantile esotropia: Eye turn inwards, appears in early infancy.
• Accommodative esotropia: Inward turning related to farsightedness and focusing.
• Intermittent exotropia: Outward drifting that comes and goes.

How is strabismus diagnosed?

Signs of strabismus should always be assessed by a pediatric ophthalmologist or orthoptist. They will perform a complete eye examination which may include:

• Medical history
• Visual acuity (reading letters from a chart or examining visual behavior in younger children)
• Eye alignment and muscle movement tests
• Binocular vision tests (to see how well the eyes work together)
• Refraction (using a series of corrective lenses to check the power of the eyes and to see if glasses are needed)
• Examination after dilating the pupils to determine internal eye structure health.

How is strabismus treated?

Treatment for strabismus will depend on the child’s age, the type and size of the misalignment, whether vision is affected, and whether there is a refractive error.

The aim of treatment is to support normal vision, improve eye alignment, and improve binocular vision and depth perception.

Treatment options for strabismus include:

Glasses

Needing glasses is a common cause of strabismus in children. If a child has a glasses prescription, wearing the correct glasses is often the first line treatment.

Treating amblyopia (a ‘lazy eye’)

If amblyopia is present (which is common in children with strabismus), then patching may encourage use of the weaker eye, improving its vision. Atropine drops are sometimes given to temporarily blur the stronger eye, and encouraging the weaker eye to develop better vision.

Prisms

This is a type if lens that bends the light entering the eye to relieve the symptoms of double vision (more commonly used in older children and adult).

Surgery

Strabismus surgery adjusts the position or strength of one or more of the eye muscles to improve alignment.

If you think your child may have strabismus, always see a pediatric ophthalmologist as successful treatments are available.

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