Strabismus (squint)

Generally, strabismus (squint) is caused by a miscommunication between the muscles around your eyes and your brain. However, sometimes, there is an issue with the actual eye muscle.

Either way, when your eyes are sending two images to the brain in childhood, your brain will learn to ignore the image from your weaker eye. This can result in a lazy eye, when one eye doesn’t see as well as the other.  

The underlying causes of this miscommunication between your eye muscles and your brain vary depending on whether the condition is present in an adult or a child. In children, if the condition is present within the first few months of life, the cause is sometimes unknown (known as infantile strabismus). However, there is often a family history of strabismus so genetic causes are likely. If a child develops strabismus aged two to four years, it is most likely to be caused by long-sightedness. Strabismus is more common in children with developmental problems such as Down syndrome or cerebral palsy.

In turn, adults may develop strabismus due to a range of conditions, including:

• short-sightedness
• stroke
• head injury
• brain tumours or hydrocephalus (increased pressure in the brain)
• neurological problems
• thyroid eye disease (related to Graves’ disease, where there is overproduction of the thyroid hormone)
• myasthenia gravis (a muscle weakness problem)

Many patients with a squint will have an assessment by the orthoptist at The London Clinic Eye Centre before seeing a consultant.

Orthoptists are professionals who measure and plot eye movements to help the consultant diagnose the problem and assess whether, for example, exercises or a prism in glasses might be needed.

The orthoptist may use tests and tools including:

• Hess charting
• synoptophore
• prism adaptation
• stereopsis
• motor fusion tests

These tests will help assess how sharp your vision is, the way your eyes focus and move together, how your eyes focus light with a series of corrective lenses and review your general eye health.

Wondering if you might have strabismus? Book an appointment with one of the specialists at The London Clinic Eye Centre today.

* We offer fast appointments Monday – Friday only.

At The London Clinic Eye Centre, we understand the impact a squint can have on your quality of life, and our expert team of consultants is dedicated to diagnosing and addressing the underlying causes of your concern to provide effective treatment options.

Currently, only adults with strabismus are treated by the consultants at The London Clinic Eye Centre. Children who have been assessed by our specialist consultants are treated elsewhere.

The treatments for strabismus include:

• Glasses or contact lenses – if your strabismus is caused by refractive errors (short-sightedness or long-sightedness), corrective lenses may help to straighten your eyes
• Prism lenses – these are special lenses that can bend the light entering your eye to reduce your eye’s inward or outward turn
• Eye patches – if you have a lazy eye caused by strabismus, or if a lazy eye is causing strabismus, placing a patch over the unaffected eye can force the connections between the lazy eye and the brain to rebuild until the lazy eye begins to work again (in children)
• Eye drops – specific eye drops work similarly to an eye patch by blurring the vision in your stronger eye to help improve lazy eye (in children)
• Botox injections – Botox injections can weaken the overacting eye muscle and cause the eye to turn
• Orthoptics (eye exercises) – your ophthalmologist may recommend certain eye exercises, alongside other treatments, to try and improve your eye’s coordination and alignment
• Surgery – during a 20-minute procedure, your surgeon will reposition the muscles around the eyeball to make the misdirected eye point in the same direction as the other eye

Find out more about potential treatments on our strabismus treatments page.

Strabismus (squint) is categorised based on the direction in which the eye is turned:

• esotropia – inward turning
• exotropia – outward turning
• hypertropia – upward turning
• hypotropia – downward turning

The condition commonly occurs in childhood and affects around one in twenty children. However, it can also begin in adulthood, depending on the underlying cause. Because both eyes must aim at the same spot together to see properly, strabismus can have a detrimental effect on your vision.