Squints (Strabismus)

A squint, also known as strabismus, is a condition where the eyes are not looking in the same direction.

While one eye looks straight ahead, the squinting eye may turn inwards (convergent squint), outwards (divergent squint) upwards or downwards. This condition can happen at any age. It may run in families, but many people with strabismus have no relatives with this problem. 

Illustration: Convergent squint

Illustration: Divergent squint

Squints can be present all the time or be intermittent, occurring in certain situations, like when the child is reading, tired, daydreaming or looking in the distance. The eye that is misaligned may be always in the same eye or alternate between each eye.

A squint can result in defective binocular or stereovision (3D vision). Children with squints can also develop lazy eye (medically termed “amblyopia”) where vision in the eye fails to develop properly.

Parents will often notice that their child’s eyes may be poorly coordinated or not aligned. In certain types of squints, the child may close one eye to obscure a double image or tilt his or her head to achieve better alignment.
Many Asian children often appear to have a convergent squint as a result of a prominent skin fold that covers the inner part of the eye, causing the eyes to appear to turn inwards (towards the nasal bridge). This is a pseudo squint, and no treatment is necessary. Your child’s paediatrician or doctor will often be able to tell you whether your child has a true or pseudo squint and will refer him or her to an ophthalmologist for further assessment and treatment, if necessary.

Unfortunately, squints cannot be prevented. However, early detection and intervention may help to prevent it from worsening or prevent complications such as the development of amblyopia (or lazy eye).

What are the causes of squint in children?
A squint is commonly caused by an imbalance in the way the brain controls the eyes. It can also be caused by abnormally high spectacle power, e.g. hyperopia (long-sightedness), or anything that obscures the vision in one eye (e.g. childhood cataracts, droopy eyelids). Occasionally, it may be due to an abnormality of the nerves supporting the eye muscles, or an abnormality in the eye muscles or surrounding tissue within the eye socket.

A squint can be diagnosed during an eye examination. It is advised that you bring your child for a complete eye exam by an ophthalmologist if you suspect he or she has a squint, or if there is a family history of squint or amblyopia.

Treatment varies with the type of squint present. In some, non-medical treatment (e.g. spectacles, eye patching, eye exercises, etc.) are more appropriate; while in others, eye muscle surgery is necessary.

As squints may occasionally be associated with an underlying brain or eye problem, the ophthalmologist would perform a thorough eye examination to exclude such problems.

Why is this procedure needed?
The aim of the procedure is to re-align the eyes so as to either:

1. Improve the ability of the eyes to work together (improve binocularity), or
2. reduce or eliminate double vision, or
3. reduce or eliminate an abnormal head position (e.g. head turn or tilt), or
4. improve the appearance of the patient
   

What does it involve?

1. There are many different surgical procedures depending on the type of squints.
2. The procedure may be done under general anaesthesia (i.e. with the patient fully asleep); or under topical anaesthesia (i.e. with eye numbing eye drops) in older, co-operative patients.
3. An incision is made on the conjunctiva (i.e. the transparent layer of membrane covering the white part of the eye) and eye muscles are located under this membrane, and repositioned (i.e. either moved or shortened).
4. Absorbable sutures are used in most cases and these will dissolve, without requiring removal, in two to three months. Non-absorbable sutures may also be used in special circumstances.
5. The conjunctiva is then repositioned over the surgical site with absorbable sutures. 

What precautions must be taken before the squint operation?
Please inform your doctor if your child has any medical illnesses.

1. A history of allergy or reaction to any medications, drugs, or food.      
2. A history of bleeding or clotting disorders, or if your child is taking any drugs or herbs that thin the blood (e.g. warfarin, aspirin, ticlopidine, or clopidogrel), which may increase the risk of bleeding.
3. Inform the doctor if your child is unwell a few days before surgery.
4. Adhere to the fasting guidelines provided.

1. The eyes may or may not be padded after the surgery. If padded, it may be left for a few hours after the operation.
2. There may be blood in the tears and the eyes may be crusted together in the mornings after waking up for a few days post-operation.
3. Eye redness may last for a few weeks after the procedure.
4. Eye pain or discomfort (e.g. a prickly, irritated sensation) is expected for a few days so the patient is advised to take oral painkillers if required.
5. Double vision may be experienced in the first few weeks, although it will improve in most of the cases.
6. Your child may also be required to administer eye drops containing an antibiotic and anti-inflammatory agent for several weeks after the operation.
7. Avoid swimming and strenuous physical activity for at least four weeks after the operation.
8. A follow-up date will be organised after your child’s operation when the vision, eye pressure and eye alignment will be assessed.

In the long term, eye alignment may remain stable, or can change. If alignment is not ideal or if double vision develops or persists, or if late drift of the eyes occur, future surgery may be required.