Strabismus

Strabismus is a condition whereby there is a deviation of the eyes. The term is used to describe eyes that are not straight or properly aligned. The misalignment results from the failure of the eye muscles to work together.

One eye, or sometimes both, may turn in (convergent squint), turn out (divergent squint), turn up or turn down. Sometimes, more than one ‘turn’ is present.

The deviation may be constant or may come and go (intermittent). In young children, strabismus may vary not only from day-to-day, but during the course of a day.

Strabismus can affect people of all ages. It may be present at birth, it may become apparent at a later age or it may appear at any time as a result of illness or an accident.

There are many causes of strabismus, including congenital reasons, paralysis of eye muscles due to nerve damage (nerve palsy), refractive errors, trauma, stroke, infections and eye tumours.

Strabismus in children

At birth, an infant’s eyes do not always focus directly on objects. They may appear to move independently of each other, sometimes crossing and sometimes wandering outward. But by the age of 3-4 months, an infant’s eyes should be able to focus on small objects and the eyes should be straight or parallel. A 6-month-old infant should be able to focus on both distant and close objects.

If parents notice crossed eyes persisting in a child at 4 months of age, they should immediately take the child to an ophthalmologist for an examination. Early medical attention is recommended for one important reason – to rule out the presence of a serious eye disease, such as retinoblastoma (eye tumour) or childhood cataract.

Regular check-ups are important

During regular check-ups, from birth to 2 years of age, paediatricians should use history and a vision evaluation to see if vision problems exist. If there is any concern of an eye or vision problem, the child should be referred to an ophthalmologist.

Strabismus is common

It is estimated that 2% of children worldwide have strabismus. The Refractive Error Study in Children (a WHO-sponsored study) in Gombak, Selangor, confirmed a similar percentage in Malaysia, with 50% of the affected children born with the condition.

It is critical that this condition be diagnosed and corrected at an early age as children with uncorrected strabismus may go on to develop amblyopia (lazy eye).

Also, a child with strabismus is more likely to be teased or bullied at school, often resulting in psycho-social problems.

When it’s not strabismus

Certain children may appear to have strabismus when, in fact, they do not. An extra fold of skin near the inner eye, a broad, flat nose or eyes that are unusually close together may produce the effect of false (or pseudo) strabismus.

False strabismus should disappear as the child’s face grows. This is particularly common in children of Chinese origin. After an examination by an eye doctor, a parent’s concern can be quickly dispelled if false strabismus is present.

Strabismus in adults

Most adults with strabismus have childhood on-set strabismus that was not treated. However, some adults have strabismus later in life due to an accident or an illness such as diabetes, cardiovascular disease or stroke. Often, the adult will experience double-vision, which is very debilitating and requires treatment.

Psycho-social effects of strabismus

Recent studies indicate that misaligned eyes can hinder social interaction, self-confidence and job opportunities. Children with strabismus are often perceived to be less intelligent and are often bullied by their friends.

Many adults also have a less favourable impression of children with strabismus. Children with strabismus often have low self-esteem, which can have long-term psycho-social effects continuing into adulthood.

Adults with strabismus often feel discriminated at work or during job interviews.

Eyes can be straightened at any age and should be seriously considered as it can enhance the patient’s quality of life.

Treatment for strabismus

Strabismus cannot be out-grown, nor will it improve by itself. Treatment to straighten the eyes is required.

There are several treatments available, and they may be used alone or in combination, depending on the type of strabismus and the cause.

  • Glasses are commonly prescribed to improve focusing and to redirect the line of sight, enabling the eyes to straighten.

  • Medication in the form of eye drops or ointment may be used, with or without glasses. Injected medication may be used to selectively weaken an overactive eye muscle.

  • Surgery may be performed if non-surgical means are unsuccessful. It is used to align the eyes by modifying one or more extravocular muscles in the eyes. It also attempts to change the position or length of muscle.

  • Eye exercises are designed to correct eye movements and may be useful either before or after surgery.

Eye alignment surgery

Eye alignment surgery improves eye function in most patients and can lead to social and economic benefits. Every surgical procedure has some risks. For strabismus surgery, the most common risks are residual misalignment and double-vision (usually temporary).

Fortunately, the more serious risks of anaesthetic complications, infection, bleeding, retinal detachment and decreased vision are very rare.

Health risks depend on the general health of the individual. For those in poor health, surgery under local anaesthesia (instead of general anaesthesia) or botulinum toxin injections may be considered.

Most individuals experience significant improvement in eye alignment with one surgery. Occasionally, surgery is only partially successful and additional surgery may be indicated.

Discomfort after eye muscle surgery is usually a foreign-body sensation in the eye lasting several days. Over-the-counter pain medication can reduce the discomfort, although stronger drugs are sometimes prescribed.

Eye alignment surgery is usually performed as a day-care procedure, although the need for hospitalisation depends on the patient’s general health and surgeon preference. Most patients return to normal activities within a few days of surgery.