Strabismus Surgery


Squint is the common name for ‘strabismus’ which is the medical term used to describe eyes that are not pointing in the same direction. You may have heard it called ‘lazy eye’ or ‘cast’ or according to the direction of the turn of the eye.

Why do squints develop?

There are a number of reasons. The main ones are:

  • Refractive (focusing abnormality)
  • Eye muscle imbalance

Effects of Squints

The brain normally combines the slightly different images from each to give a 3-D picture of the world. When a squint is present (strabismus), the eyes point in different directions and the brain is no longer able to do this.


The brain then ignores the image from one eye and the vision in this eye may deteriorate (amblyopia). When an eye is turned in the squint is said to be convergent (esotropia) and when turned out it is divergent (exotropia). Some patients may also have a vertical squint, where one eye is higher than the other. The squint may be present all or only part of the time (constant or intermittent) and may appear to affect only one eye or alternate between the eyes.

The most obvious sign of a squint is one eye that does not look straight ahead but turns inwards, outwards, upwards or downwards.

Minor squints may be less obvious.

Babies and Young Children

It is quite normal for the eyes of newborn babies to ‘cross’ occasionally, particularly when they are tired. Speak to your ophthalmologist if you notice this happening to your child after the age of three months.

If your child looks at you with one eye closed or with their head turned to one side, it may mean that they are experiencing double vision and could be a sign that they have a squint. See your ophthalmologist as soon as possible if this happens repeatedly.

Lazy Eye

If a squint is left untreated, lazy eye (amblyopia) can develop. The vision in the affected eye gradually deteriorates because the brain ignores the weaker message being sent from that eye. It is not usually possible to correct amblyopia after the age of about seven years, which is why it is so important to treat a squint as soon as possible.


1. How will the squint be managed?

The first step is to prescribe glasses if there is a significant refractive error and this may also improve the squint. Patching or atropine drops are used to treat amblyopia if present. Squint surgery can be used to improve the alignment of the eyes and in some children can restore some binocular function if done early.

2. Refractive Abnormality and Spectacles

The main refractive (focusing) error that may be causing the of convergent squint is hypermetropia (long sight). Full correction of refractive error may correct the squint eye.

3. Will my child need to wear glasses?

This is decided by the ophthalmologist (the eye surgeon responsible for the management of your child’s squint) after refraction

4. Eye Muscle Imbalance and Occlusion (Patching)

In order to focus both eyes on an object all the eye muscles of each eye must be balanced and work together. When one eye turns that eye is not focused properly and the vision can deteriorate in the squinting eye. An orthoptist carries out a series of eye tests to determine the presence of a squint and measure vision. In some children who develop a squint patching or using atropine in the good eye will make the lazy eye work harder and therefore improve the vision.

5. How does a patch affect the squint?

Patching purely improves vision by making the brain use the amblyopic eye. The unpatched eye will appear to be straight while the patch is worn. Sometimes when the patch is removed the squint may be temporarily more noticeable, but later returns to the pre-patching position.

6. Will my child need to wear a patch?

Possibly, if your child is less than eight years and if the vision in one eye is reduced because of the squint. This will mean regular follow up visits.

7. Which eye does the patch need to be put on?

On the straight eye so that the eye with the poorer vision is used on its own for some part every day. It is a very effective way of improving vision.

8. Does my child wear his glasses with the patch?

Yes, the patch should be worn on the face. It is made from non-irritating material to prevent rashes. Spectacles are worn over the patch.

9. Atropine

Another way of getting a lazy eye to work is putting atropine into the good eye to blur the vision and make the weaker eye work harder.

10. Can eye exercises cure the squint?

They can hep to control some intermittent squints in older children.


Will an operation help?

Many children with squints do need an operation as well as glasses or patching. The operation is confined entirely to the surface of the eye. The muscles which are attached to the outside of the eye are moved to a new position on the surface of the eye. Usually the muscles of the squinting eye are operated on, but sometimes it may be necessary to operate on the muscles of the other eye as well, as this may give better results. Often one operation is effective but some children will need further operations. Even an operation cannot ensure perfect alignment afterwards. In any squint surgery the focusing parts of the eye are never operated on and there is no significant risk of your child’s sight being damaged by the operation.

Can you tell us about the hospital stay?

On the day of admission your child will be seen by the your surgeon and the anaesthetist (the doctor who puts your child to sleep for the operation).

Before returning home, the nurse will clean around the child’s eye and administer drops. The doctor will see your child and ensure they are fit for discharge. An appointment will be made for follow-up after this. Usually drops will need to be used at home. The nursing staff will show you how to administer drops.

Frequently Asked Questions

Is squint common?

About 2-3% of the population have a squint.

Is my child too young to start treatment?

No, the earlier the better.

Does it matter if the squint is not treated?


  • If at some later point the sight in the better eye is lost e.g., by accident, the squinting eye will not be able to compensate and your child would be visually handicapped
  • Your child will NOT grow out of the squint
  • Sight will get worse in the affected eye
  • Your child may be teased about their appearance
  • Your child may be precluded from some jobs later if they have a lazy eye