Also known as Strabismus

Squints is a visual problem in which the eyes do not look in the same direction. One eye may look straight ahead, while the other eye turns inward, outward, upward, or downward. It may happen all the time or only when the person is tired, unwell or focusing on a near or distant object.

On this page, you can find the following information:

Key points 

  1. Squints (strabismus) is when the eyes do not look in the same direction.
  2. Left untreated, squints can lead to eye problems such as lazy eye and double vision.
  3. Treatment options include patches, glasses and eye muscle surgery.
  4. The aim of treatment is to get both eyes aligned and working equally.


  • Squints can tend to run in families.
  • They may arise in the first few months of life or they may appear later in childhood.
  • In early onset squint, the child has a poor ability to use the eyes together (known as binocular vision).
  • In later-onset squints, binocular vision is quickly lost.
  • If a child is long-sighted, the effort to focus clearly may lead to a squint. Glasses alone may correct this problem.

Very occasionally, a child may develop a squint because an eye is abnormal and there is a problem with sight. The earlier this is detected the sooner treatment can be started. If a child squints with one eye, the vision in that eye will become lazy. This is because the brain learns to ignore information coming from the squinting eye.

Squints can also be seen in adults, as a long-standing problem or caused by temporary nerve palsy (a weakness or dysfunction of a nerve that usually fades over time).

If left untreated, squints may:

  • cause a child to develop a lazy eye, (poor visual development) which if not corrected will lead to poor sight in that eye
  • cause a child to lose binocular vision
  • cause adults to develop double vision
  • affect physical appearance.


Some babies look like they have a squint due to the wide bridge of their nose. As they grow, their features develop and this appearance goes away. However, a child with a true squint will not grow out of it. To be on the safe side, all children suspected of a squint must be seen by an eye specialist. No child is too young to be seen.

In adults, a squint from a nerve palsy may recover on its own and treatment is therefore only undertaken once the squint has stabilised.


Glasses will be prescribed if there is a focusing error, particularly with long-sightedness. If a child squints with one eye only, then this eye will become lazy. To fix this, the other eye is patched so the child has to use the ‘lazy’ eye. The aim is to build the vision in the lazy eye to achieve a state where the child will use either eye to see. The squint will then switch from one eye to the other. This is called alternation.

If the appearance of a squint is obvious then surgery is carried out to move the eye muscles and thereby straighten the eye. In some cases surgery is performed early in an effort to achieve binocular single vision.

Eye muscle surgery (strabismus surgery)

Eye muscle surgery involves altering the position of some of these muscles, in order to realign the eyes. It is most commonly performed for an in-turning or out-turning eye; however, it may be used for vertical or rotational imbalances as well.

The information provided here gives a general overview of eye muscle surgery. If you are needing eye surgery, talk with your doctor or eye specialist to make sure you understand what is needed in your particular case.

Squint surgery is performed as a day stay procedure under general anaesthesia.

  • In children, surgery is usually performed between the ages of six months and four years.
  • In adults, it may be performed at any convenient time once the squint has stabilised.

The operation

During surgery, eye muscles can be:

  • Weakened – This usually involves shifting the position where the muscle inserts into the eye to a position further back on the eye. This works to slacken the pull of the muscle on the eye and allows the muscle tissue to relax more.
  • Tightened – Muscles are tightened by removing a piece of the muscle near where it inserts into the eye and then reinserting the muscle into its original location. By removing a piece of muscle the muscle is shortened and therefore strengthened.
  • Repositioned – For some strabismus problems the eye muscles are neither weakened nor strengthened but repositioned. For example,  the insertion is moved to a different location to provide a different action on the eye.

Eye muscle surgery is usually performed:

  • Under general anaesthesia. In some circumstances it can be performed under local anaesthesia. No overnight stay in hospital is required.
  • On both eyes at once. Even if it tends to be one eye that turns in or out more often than the other, surgery is usually split between the two eyes. The aim of surgery is to achieve good alignment of the eyes. This can be obtained by doing a lot of surgery on one eye or less on two eyes. Often the latter is the best option.

At the end of the operation local anaesthesia is injected around the eyes to try to have the eye numb when you wake up. This anaesthetic wears off over a few hours. It is fine to take paracetamol or other pain killers but you probably won't need them beyond the first day.

Post-operative care

Use of eye drops

After surgery, eye drops are required until the first post-operative check-up, one week later. If the eye is settling nicely, then the eye drops will be stopped at that stage. A further post-operative appointment will be made for six or eight weeks later, by which time the results of the surgery can be clearly seen.

How eyes will look and feel

After surgery, the eyes are usually a little red and watery. There may be some haemorrhage (bleeding) under the conjunctival membrane over the white of the eye. This will settle over two to three weeks. It usually takes on a yellowish discolouration, like a bruise, as it clears.

Sometimes there is some thickening of the membranes over the eye which can take several more weeks to smooth over. Very fine dissolving sutures are used to reposition the conjunctival membrane at the end of surgery. Until these sutures dissolve there may well be some scratchiness in the eyes. This usually disappears over two or three weeks.

Keep eyes dry

After surgery water should be kept out of the eyes for a couple of days. Be careful to keep the eyes dry during showering/bathing. Avoid swimming for a week. All other normal activities, including heavy exercise, can be resumed two days after surgery. Use of the eye for reading, watching TV, etc, will not cause any problems with the surgery.

Risks of surgery

As with any operation, eye muscle surgery carries the risk of complications. These include:

Unsatisfactory alignment of eyes

This is the major risk of eye muscle surgery. It may be an under-correction (the eye still turning slightly in the same direction as it was originally), or an over-correction (with the eyes now turning the other way).

Typically, an under-correction is more common than an over-correction. Obviously, every effort is made to achieve perfect alignment but this is not always possible. If the alignment is still unsatisfactory at the final post-operative visit, further surgery may be required.

Double vision

This not uncommon in the initial stages after surgery. It usually occurs because there has been an over-correction. Often this will sort itself out within a few days to weeks. If it fails to get better by the final post-operative visit, further surgery may be needed.


This an unusual post-operative complication which usually responds well to antibiotic drops. Infection should be considered if you develop discharge or increasing redness and discomfort post-operatively. Please contact your doctor if you are concerned.


Because a cut is made through the conjunctiva and muscle there is always some residual scarring. Usually this can be seen only through a microscope. However, it may be possible to see it on close examination, particularly if you know it should be there.

Loss of vision

As with any eye surgery, there is a theoretical risk of visual loss from eye muscle operations, but this is a very, very rarecomplication. If you have any questions about your operation please don't hesitate to contact your surgeon.

Learn more

Baby's eyes Kids Health NZ, 2013
Squints (Strabismus) in adults Eye Doctors NZ

Credits: Editorial team. Reviewed By: Adam May