Strabismus or squint is a condition where the eyes are misaligned and point or look in different directions. One eye may look straight ahead, while the other turns inward, outward, upward or downward.

Strabismus may be constant, or it may be intermittent (comes and goes). The eye that is turned or misaligned may switch or alternate.

Strabismus is often seen in children, but it can also occur later in life. It occurs equally in males and females, and it may run in families.

Understanding strabismus:
How our eyes work together

In normal cases, both eyes look or aim at the same spot. The brain then combines the images formed in each eye into a single, three-dimensional (3D) image. This 3D image gives us depth perception.

When one eye is looking the other way and is out of alignment, two very different images are sent to the brain. In a young child, the brain learns to ignore the image in the misaligned eye, and sees only the image from the eye that is looking straight. The eye that is misaligned then becomes amblyopic (lazy), and the child loses depth perception or 3D vision. Adults who suddenly develop strabismus often have double vision (diplopia) because their brains cannot ignore the different images from both eyes. Children usually do not see double.

Early detection and treatment of eye conditions are key to the optimal preservation of sight.

Schedule an assessment should you experience any eye discomfort or vision problems.

What causes

Six eye muscles controlling eye movement are attached to the outside of each eye. All the muscles in each eye must be balanced and working together to focus both eyes on a single target. The brain controls these eye muscles.

The exact cause of strabismus is not fully understood. Most children with strabismus are otherwise normal with no other eye problems. Some have a family history of strabismus.

Some disorders of the brain may cause strabismus. These include:

  • Cerebral palsy
  • Down syndrome
  • Hydrocephalus
  • Brain tumours
  • Prematurity

Some eye conditions, especially if occurring in only one eye, or asymmetrically (unequally), can cause strabismus. These include

  • Dense cataract
  • Eye injury
  • High refractive error

How is
strabismus diagnosed?

Strabismus can be diagnosed during an eye examination. If you suspect that your child has misaligned eyes, do get him or her to see an eye doctor for an examination.

What are the
common types of strabismus?

Congenital Esotropia

In this condition, the eye turns inward. It is the commonest type of strabismus in infants. Surgery is usually required.

Accommodative Esotropia

This occurs in children usually 2 years or older. When the child focuses on an object to see clearly, the eyes turn inward. This can occur when the child focuses to look at distant objects, near objects or both.


This is an outward turning of the eye, often when the child is focusing on distant objects or relaxes his eyes in a “dreamy” state. It can also occur when the child is tired or unwell.

How does Amblyopia (“Lazy” Eye)
develop in strabismus?

When both eyes are in alignment, good vision develops during childhood. When one eye is misaligned, amblyopia develops in the misaligned eye.

The brain pays attention to the image in the eye that is looking straight, and ignores the image of the misaligned eye. If this eye is consistently and repeatedly ignored during early childhood, the eye may fail to develop good vision, or may even lose vision. Strabismic amblyopia then develops.

How is
strabismus treated?

Treatment options include glasses, exercises, prisms or surgery.

In accommodative esotropia, glasses (sometimes bifocals) may be prescribed to reduce the focusing effort and thus straighten the eyes.

Covering or patching the good eye is often necessary to treat amblyopia.

All about
strabismus surgery

The eye muscles controlling movement of the eye are detached from the wall of the eye and repositioned during the surgery. Only the muscles responsible for turning the eye abnormally will be operated on. It may be necessary to perform surgery on one or both eyes, depending on the type and severity of the strabismus.

When performed on children, usually general anaesthesia is required. In adults, local anaesthesia can be performed in some cases.

After surgery, glasses may be required. Occasionally, more than one operation may be needed to get the eyes aligned.

Strabismus surgery is safe, but some of the risks include bleeding, scarring and infection. Very rarely, loss of vision may occur


This is a condition where the eye of a young child appears to be turned in or crossed, when in actual fact they are not. Young children, often of Oriental or Chinese lineage often have wide, flat nasal bridges and a fold of skin at the inner eyelid that gives the illusion that the eyes are turning inward.

The appearance of pseudostrabismus will usually improve as the child grows older and the facial features change.

If you think your child’s eyes are turning inwards, it is better not to assume that it is a pseudostrabismus. Bring him or her to an eye doctor to have a check to distinguish it from a true strabismus.