Strabismus (Squint)

Strabismus (commonly known as a squint) is a visual defect in which the eyes are misaligned and point in different directions. One eye may look straight ahead, while the other eye turns inward, outward, upward or downward.

About 3-4% of all children are born with strabismus, making it a common condition in New Zealand. Strabismus occurs equally in males and females. They may run in families; however, many people with strabismus have no relatives with the condition.

The exact cause is not fully understood. Any factors influencing the brain’s control of binocular vision or the eye muscle functions can cause it. Occasionally, children with Down Syndrome, brain tumours or infections can present with strabismus.

The main indication is that an eye is not straight. Sometimes, the child may squint an eye to see or tilt their head to see. Favouring one eye over the other can lead to amblyopia (lazy eye), which will lead to long-term poor sight in that eye.

This is when the eye of an infant appears to be crossed, though they actually are not. This is often due to a wide, flat nose, or a fold of skin in the inner lids making the eyes appear crossed. Children often grow out of pseudoesotropia but they never grow out of a true esotropia.

Infantile esotropia

Infantile esotropia, where the eye turns inward, is the most common type of strabismus in infants and it usually occurs between 3–6 months of age. The correct treatment for infantile esotropia is early intervention with surgery. This restores the eyes to their normal alignment and it also gives the child a better chance to develop the ability to use two eyes together (3D vision).

Accommodative esotropia

Accommodative esotropia is a common form of strabismus and often occurs in children two years of age or older. The eye turns inward due to excessive use of accommodative effort for better vision.  It can present when the child is looking at distant or near objects. Often children with this condition are farsighted — wearing appropriate corrective glasses helps with the control of misalignment. Sometimes, children will need eye muscle surgery to correct the misalignment.

Exotropia

Exotropia refers to the outward turning of the eye. This type of strabismus more often occurs when the child is looking at far (distance) objects, though it can occur for any distance visual fixation. It becomes more noticeable when the child is tired or sick. Exotropia often needs surgical correction if it becomes constant or noticeable for the majority of the time during the day.

After a complete medical eye examination, the child may be prescribed glasses as a treatment for the strabismus and also, more importantly, to improve the child’s vision.

If glasses cannot control the strabismus or are not needed, then eye muscle surgery will be recommended to restore normal alignment and binocular vision.

Strabismus surgery on children is carried out as a day-stay procedure performed under a general anaesthetic. The eye muscle causing the eye to turn inward or outward is ‘loosened’ or ‘tightened’ as required. The eyes are not normally patched, and recovery is fast, so the child can resume normal activities within a few days.