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Everything You Need to Know About Strabismus or 'Crossed Eyes'

What Is Strabismus?


Strabismus, or crossed eyes, is a condition where one of your eyes is misaligned - i.e. it looks in the wrong direction. There are multiple forms of strabismus; one eye can be inward (esotropia, "crossed eyes" or "cross-eyed"), outward (exotropia or "wall-eyed"), upward (hypertropia) or downward (hypotropia).

Strabismus can be constant or intermittent. The misalignment might always affect the same eye (unilateral strabismus), or both your eyes may take turns being misaligned (alternating strabismus).

To prevent double vision from genetic and childhood strabismus, the brain ignores the misaligned visual input, which typically leads to amblyopia or "lazy eye" in the affected eye.


Strabismus Symptoms


The primary sign of strabismus is a visible misalignment of the eyes, with one eye facing in, out, up, down or at an oblique angle.

Typically, constant strabismus does not cause symptoms like eye strain and headaches as there is practically no attempt by the brain to straighten the eyes. Because of this, large-angle (extreme) strabismus usually causes severe amblyopia in the misaligned eye if left untreated.

Less noticeable cases of small-angle strabismus are more likely to cause disruptive visual symptoms, especially if the strabismus is intermittent or alternating. In addition to headaches and eye strain, symptoms may include an inability to read comfortably, fatigue when reading and unstable vision. If small-angle strabismus is constant and unilateral, it can lead to significant amblyopia in the misaligned eye.

Newborns often have intermittent crossed eyes due to incomplete vision development, but this usually disappears as the infant grows and the visual system continues to mature. Most types of strabismus, however, do not disappear as a child grows.


What Causes Strabismus?


Each eye has six external muscles, called the extraocular muscles, that control eye position and movement. For normal vision, the position, function and control of these muscles for both eyes must be coordinated perfectly.

Strabismus occurs when there are problems that interfere with the control and function of the extraocular muscles. The problem may originate in the muscles themselves, or in the nerves or vision centres in the brain that control binocular vision.

Genetics can also play a role: If you or your partner has strabismus, your children have a greater risk of developing strabismus as well.


What To Expect After Strabismus Surgery


Your eyes will be red and somewhat sore after strabismus surgery. You will probably see some blood in the surgical area, usually toward the corners of the eye. This is to be expected and is equivalent to a small bruise.

Any broken blood vessels in the eye and general eye redness should fade within two to three weeks. You may feel like there is something in your eye, but this sensation will subside. Usually you can resume normal activities within a few days.

Children younger than 10 will very likely need a second or third strabismus procedure to maintain the best possible eye alignment. In some cases, eyeglasses or special lenses (prisms) placed in a pair of glasses may help to coordinate the way the eyes work together.


How Long Does Double Vision Last After Strabismus Surgery?


During the first few days after surgery, eye alignment is a good indicator of the final outcome. However, more permanent results may not be known until a few weeks after surgery. You may experience double vision throughout this period, but it should not persist after a successful operation.


Read more about eye health from our article selection here, or consult our ‘Ask the Optician’ eye health FAQs here.