Strabismus (Squint)

What is strabismus?

Strabismus, also known as a squint or an eye turn, is a condition where the eyes are misaligned and are pointing in different directions. This leads to both eyes seeing two different images, as both eyes are seeing the world from two different angles.

Depending on the age of strabismus onset, the amount of time strabismus has been present, and the type of strabismus, the brain may either:

Learn to ignore the image from the eye that is turning, and over time, can lead to a condition called amblyopia or lazy eye. This usually happens when strabismus is present during the period of development (i.e. 8 years old and younger).
Experience double vision.

There are different types of strabismus. This will differ based on:

The direction of the eye turn
Whether one eye or both eyes are turning
What age the turn started
The duration of the eye turn
How often the eye turns
Whether the turn alternates between both eyes

Your doctor will discuss with you what type of strabismus you have, as well as its effects on your vision, after a series of investigations. It’s important to investigate the type of strabismus you have, as this can change the type of treatment you need.

Causes of strabismus

Each eye is surrounded by six muscles – each one in charge of moving our eyes in a certain direction. Strabismus happens when one or more of these muscles aren’t working properly, leading to an imbalance in the pull of the other muscles, and thus causing the eye to turn. This can be caused by a variety of things, the most common one being the brain being unable to control the eye muscles properly, the mechanism for which is not clearly understood. It can also be due to something blocking one of the muscles from moving (e.g. tumours), or injury to one of the muscles due to trauma. Different medical conditions (e.g. stroke, diabetes, thyroid problems) can also affect the eye muscles, by directly affecting the muscles, affecting the brain controlling them, or affecting any of the wirings (i.e. nerves) that connect the eye to the brain. Stress and infections can also make strabismus more obvious. Additionally, strabismus can be inherited from previous generations. There is a higher chance of having strabismus if someone in your family also has the condition.

Early diagnosis of strabismus

Early detection of strabismus gives you a better chance of a more favourable outcome after treatment. This is especially true for children within the age of visual development (under 8 years old), as the vision centres in the brain are still developing during this time. In adults, early detection is also important, as there may be another medical condition or a tumour causing the eye turn that needs to be addressed promptly.

Management of strabismus

Treatment of strabismus is varied based on the type of strabismus you have and your age. Examples of treatment include:

Prescription glasses or contact lenses
Strabismus surgery
Injection of botox to weaken a muscle
Prism lenses
Eye exercises
Patching, if there is an associated amblyopia or lazy eye with the eye turn
Occluding one eye

If the cause of strabismus is known, your doctor may decide to treat the cause first if possible, as this may sometimes be enough to allow the eyes to correct themselves. Strabismus management may also be accompanied by other treatments depending on whether there is an accompanying condition to the eye turn, such as lazy eye. Sometimes in infants less than 4 months, strabismus spontaneously resolves as the baby develops, in which case will not need treatment.

Not all treatment options will be viable on all types of strabismus. Your doctor will advise you on what treatment is best for you.

Why do we treat strabismus?