squints

Squints (Strabismus) - What it is

Strabismus, also known as a squint, 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.

Illustration: Inward drifting of the right eye (Convergent squint)

Illustration: Outward drifting of the right eye (Divergent squint)

Strabismus can develop at any age, it might be present within the first few months of life or only occur in adulthood. The drifting of the eye may be present all the time or may only be observed intermittently, occurring in certain situations like when the individual is tired, daydreaming, or looking into the distance or reading. The eye that is drifting may always be the same eye or alternate between each eye.

Having strabismus may also result in poor depth perception and an inability to appreciate 3-dimensional images. Children with squints can also develop lazy eye (medically termed "amblyopia") where vision in the eye fails to develop properly.

Squints (Strabismus) - Symptoms

For children with strabismus, 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 or tilt his/her head to compensate for the eye misalignment. Some individuals who develop strabismus in later childhood or adulthood might also experience double vision.

Many Asian children have an appearance of an in-turned eye. This is because they have a flatter nose bridge and a prominent skin fold that covers the inner aspect of their eyes. In such instances, the eyes are actually straight and merely appear closer together. This is a pseudo-squint (fake squint). No intervention is required for these cases, this in-turned eye appearance usually becomes less obvious due to changes of the face/eyelid as the child grows.

Having said that, all children who appear to have misaligned eyes should be reviewed by a doctor. Your child’s pediatrician 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.

Squints (Strabismus) - Causes and Risk Factors

Strabismus may run in families, but many people with strabismus do not have relatives with this condition. Strabismus might be caused by abnormally high spectacle power or result from vision obscuration 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 and tissue within the eye socket. Children who were born premature or individuals with certain conditions might also be at higher risks of developing strabismus.

Squints (Strabismus) - Treatments

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 and may order further investigations to exclude such problems.

Squints (Strabismus) - Preparing for surgery

Why is this procedure needed?

The aim of the procedure is to re-align the eyes so as to either:

Improve the ability of the eyes to work together (improve binocularity), or
Reduce or eliminate double vision, or
Reduce or eliminate an abnormal head posturing (e.g. head turn or tilt), or
Improve the appearance of the patient

What does it involve?

Strabismus surgery is a procedure performed on the muscles controlling eye movements. The specific type of eye muscle surgery will depend on the type of strabismus.
The surgery 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 co-operative patients.
An incision is made on the conjunctiva (i.e. the transparent layer of membrane covering the white part of the eye), then the eye muscles are located under this membrane and repositioned (i.e. either moved or shortened).
Absorbable sutures are used in most cases, these will dissolve and do not require removal. Non-absorbable sutures may also be used in special circumstances.
The conjunctiva is then repositioned over the surgical site with absorbable sutures.

What precautions must be taken before the squint operation?

When planning for surgery, please inform your doctor of all medical illnesses.

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

Squints (Strabismus) - Post-surgery care

The eyes may or may not be padded after the surgery. If padded, it may be left for a few hours after the operation.
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.
Eye redness may last for a few weeks after the procedure.
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.
Double vision may be experienced in the first few weeks, this should improve in most cases.
Eye drops containing an antibiotic and anti-inflammatory agent will need to be instilled a few weeks after the operation.
Avoid swimming and strenuous physical activity for at least four weeks after the operation.
Follow-up clinic visits will be arranged after the operation where eye alignment, vision and eye pressure will be assessed.

After strabismus surgery is completed, the improved eye alignment may remain stable or continue to change over time. If the eye alignment is not ideal, or double vision persists, or late drift of the eyes occur, future surgery may be required.