Strabismus (Squint) surgeries






  • You will soon be having a squint operation to try and straighten your eyes. This leaflet has been prepared to try and answer any questions you may have about your operation.  It will also help to make sure that you are happy to have the surgery that your doctor has discussed with you and will form part of your consent for surgery.
  • If you have read the leaflet and are still uncertain about anything then please tell your doctor or orthoptist.
  • Before you can have any operation you must give your permission or consent. To be able to do this you should understand:
    • What the operation involves.
    • What we hope it will do.
    • What are the chances of it working.
    • What are the possible risks / complications.
  • We will try to give you as much of this information as you want during your visits to the outpatient clinic. However, as part of the consent process we will need you to sign a form to say that you understand the things listed above and that you want to have the operation.
  • This form will be filed in your medical notes and you will be given a copy to keep. You will have signed to say that you have read and understood this leaflet and that you have had the chance to ask about anything of which you are unsure.
  • You can change your mind about having the operation at any time – even after you have signed the form!



  • Each eye is moved in different directions by six muscles. These muscles are like small straps which attach onto the outside of the eyeball and work like reins to move the eye left/right, up/down and rotate it.
  • Normally the brain keeps both eyes lined up together whatever direction we are looking in. This allows us to take the picture from each eye and join them together into one.  When we use both eyes together like this we are said to have ‘binocular vision’.
  • Normal binocular vision allows us to see depth between objects more easily and helps to keep the eyes straight. The process of learning to use the eyes together and develop binocular function takes from birth until about the age of seven years.
  • Sometimes the eyes are not straight and lined up together. This is called a strabismus or squint.  We will use the work squint in this leaflet to mean that the eyes are not straight (rather than meaning screwing up the eye to close it).  A squint can develop at any time from just after birth to old age.  When one eye appears to turn in we call this a convergent squint.  If the eye is turned out this is a divergent squint.  Less commonly one eye may be higher than the other or rotated.  Sometimes the turning eye varies from one to the other at different times.  In addition the squint may only be present for some of the time e.g. at certain times of day or when looking only at certain distances or in certain directions.
  • When an adult or older child who has previously had straight eyes develops a squint they will usually get double vision. Young children with squints, however, do not get double vision.  This is because a child’s brain is still developing and has the ability to ‘ignore’ the vision from the squinting eye.  Although this stops the child seeing double it also causes problems.  It stops the development of good vision in the turning eye and the sight in this eye gets gradually worse. The eye is then said to have become lazy or ‘amblyopic’.  Although the eye may be otherwise perfectly healthy, without early treatment this loss of vision may be permanent. 
  • Therefore a child who develops a squint in one eye at an early age may quickly lose sight in it and also lose the chance of ever having normal binocular vision. Fortunately we can try and treat both of these problems by patching the straight eye.
  • Wearing a patch as suggested by your doctor or orthoptist is often the most important part of treating your child’s squint.

Aim Of The Operation

  • People may have squint surgery for a number of different reasons. The commonest is to try and improve the cosmetic appearance of the squint.
  • In older children and adults it is to try and improve or get rid of double vision. Sometimes – usually only in younger children – it is to try and allow use of the two eyes together.
  • Your doctor will explain which of these we hope to achieve in your particular case.

How A Squint Operation Is Done

  • Squint surgery is a very common eye operation. It usually involves tightening or setting back one or more of the strap like muscles which move the eye.  These muscles are attached quite close to the front of the eye on the white part (sclera) and are easy to get at.
  • We do not need to take out the eye to do the operation!
  • It is important to remember to bring your glasses to hospital with you on the day of surgery or your operation may have to be cancelled.
  • Squint surgery is nearly always a day case procedure so you or your child should be in and out of hospital on the same day.
  • There are two kinds of squint operation – adjustable and non-adjustable:
  1. Non adjustable surgery

This is the most common kind of operation which we use for younger children and some adults.  The whole operation is carried out in one go under general anaesthetic i.e. with the patient asleep.  The operation usually takes about 30-60 minutes to do depending on the number of muscles we need to operate on.  As soon as the nurses and doctor are happy that you have recovered from the anaesthetic and have had something to eat you are free to go home – usually about four hours later.

  1. Adjustable surgery

Unfortunately squint surgery is not an exact science and the results can sometimes be a bit unpredictable.  This is particularly true in certain types of squint e.g. patients who have had a squint operation before, patients with a squint due to injury, patients with thyroid eye problems.  Squint surgery using an adjustable suture is a technique which can be used to try and give a better result.  However, because it involves doing some of the operation under local anaesthetic (i.e. with you awake) it is only suitable for older children and adults.



Adjustable surgery is carried out in two parts:

Part 1 – The ‘main’ operation

The main part of the operation is carried out in the operating theatre under general anaesthetic (with you asleep).  Exactly as in a non-adjustable operation the muscles are weakened or strengthened according to the size of the squint.  However, instead of fully tying the stitches attaching the muscles, we tie a bow which can be undone later if necessary.

We will then leave you to wake up from the anaesthetic back on the ward.  Any pad put on the eye at the end of the operation will be taken off to give you a period with both eyes open so that your eyes can adjust to their new position.


Part 2 – Adjusting the stitch

The final part involves undoing the bow on the sutures and either tying the knot off or adjusting the position of the muscles by either gently slackening or tightening the stitches.  Depending on which surgeon is doing your operation we will either do this back in the operating theatre or on the ward.

We will put lots of anaesthetic drops in your eye(s) to make them comfortable so that you can open them both easily and so that they will be nice and numb for the last part of the operation which will be done with you awake.

During this part of the surgery the eyelids will be gently held open by a small instrument called a speculum.  In theatre the surgeon will use the operating microscope to help him see the stitches more clearly.  This means you will face a bright light so to make you more comfortable we will put some drops in your eye to make your pupils small.  You will probably be asked to sit up from time to time and put on any glasses you may have so that we can check to see that your eyes are straighter.

At the end of the procedure you may have a pad put over the eye to wear until you get home.


After The Operation

  • After the operation the eye(s) will inevitably be a little red and sore. With non-adjustable surgery we usually put in some local anaesthetic around the muscles at the end of the operation to make things more comfortable for a few hours.  Sometimes a mild painkiller such as Paracetamol or Calpol is required later in the evening.  The soreness usually wears off within a day or two but the redness usually lasts for a few weeks – sometimes longer with adjustable and repeat squint operations.  Children especially may also be sick immediately after surgery although this is not usually the case.  The vast majority of patients will go home on the same day as surgery but occasionally someone may have to stay overnight.
  • After you go home you may be given some antibiotic eye drops to try and prevent any infection. We will then normally arrange a follow up appointment in the outpatient clinic one to two weeks later.
  • Even if the eyes appear perfectly straight after surgery it is important that children continue to attend appointments with the orthoptist. This is because they may still need to wear their glasses and/or patch.
  • The operation will not replace patching nor will it improve vision.


How Successful Is Surgery?

The success rate for squint surgery varies with the kind of squint and the reason for surgery.  Unfortunately squint surgery is not an exact science.  The amount of correction that is just right for one patient may be too much, or too little, for another with exactly the same size turn.  Although the eyes may be straight just after surgery they can sometimes drift back, either in the same or opposite direction, later on – sometimes years later.  Another operation may then be needed.  Overall about 10-15% (one in eight) of people having squint surgery may eventually undergo another operation.


Risks And Complications Of Surgery

Squint surgery is generally a simple and safe procedure.  However, as with any operation, complications can and do occur.  Generally these are relatively minor but on rare occasions they may be serious.



Commoner Complications

  • Double vision

In adults the aim of surgery is often to try and get rid of double vision.  Sometimes we may not be able to remove the double vision completely but can try to reduce it and make it less noticeable.  Occasionally, however, with the eyes in a new position after surgery, double vision may occur which was not present before surgery.  Often this will settle down by itself during the first few weeks after the operation but sometimes it persists.  Usually we can improve it with either further surgery or spectacles.  Very rarely, however, someone gets double vision after surgery which we cannot get rid of at all – even by doing another operation.  In this situation we may have to try blocking out the vision from one eye with either a frosted spectacle lens or contact lens or even a lens implanted in the eye.

As part of your examination before the operation, the orthoptist will do some tests to see if you are likely to have problems with double vision after the surgery.  If we feel that double vision is a particular risk for you we will inform you and may even suggest some extra tests before any operation – such as injection into one of the eye muscles.  Even so, double vision is always a risk with squint surgery in children aged about six years and older and in adults.


Other Minor Complications

These are not usually important and still only happen in less that one in 20-30 cases.

  • Allergy/stitches

Some patients may have a mild allergic reaction to the drops or ointment they have been given to use after surgery.  This usually results in some itching/irritation and possibly some redness and puffiness of the eyelids.  It usually settles very quickly when the drops are stopped.

During surgery we will use some stitches to re-connect the muscles to the eye and to close the small surface incisions.  Sometimes a patient produces a mild reaction to the stitch material usually resulting in a small red lump over the stitch.  Again this usually settles very quickly as the stitch dissolves or with the use of some weak steroid drops.

Occasionally the very fine stitches placed on the surface of the eye may loosen or break soon after surgery and need replacing.  In adults this can be done easily in clinic but children may require another very short general anaesthetic.  Rarely as the eye heals a small cyst can form which again may need another small operation to remove it.

  • Scarring

An incision anywhere on the body heals with some scarring and the surface of the eye is no different.  Eye scars after squint surgery are usually virtually invisible.  However, since some people produce more scarring when they heal than others, scars may occasionally be visible – but rarely unsightly – especially with repeat operations.

  • Infection

Infection is a constant risk with any operation and obviously we take all precautions we can to avoid it.  Infection after squint surgery is rare and often comprises a mild conjunctivitis.  The eye becomes slightly more red and gritty and is sticky.  It usually quickly gets better with antibiotic eye drops.  Very rarely (less than one in 1000 cases) the infection may get behind the eye.  This is a more serious problem and requires admission to hospital for a course of stronger antibiotics.


Please feel free to contact us as instructed if you are worried about possible allergy or infection before you are due back in the clinic.



Extremely Rare But Serious Complications

  • Lost muscle

Rarely (less than one in 1000 times) one of the eye muscles may slip back behind the eye either during the operation or shortly afterwards.  It is usually possible to find this ‘lost’ muscle and reattach it – sometimes we may need to get some scans of the eye first to help.  However, on rare occasions it may prove impossible to find and the eye is then likely to have very reduced movement in one direction.  This is often associated with a large squint and double vision.  It may take several more operations to try and improve things and unfortunately the result may still not be perfect.

  • Needle penetration

Because we are sewing muscles onto the surface of the eye it is possible for the needle to pass too deeply and actually enter the eye.  This occurs in less than one in 1000 cases and even then only rarely results in any serious problem.  Although further complications could then result in the vision of the eye being damaged or lost, this is extremely rare.

  • Anterior segment ischaemia

Some of the blood supplying the front of the eye travels with the eye muscles.  Therefore cutting these muscles during squint surgery can, on rare occasions, damage this supply.  This is called anterior segment ischaemia.  Severe cases are rare (less than one in 1000 cases) and occur in adults who often have certain risk factors.  However, it can result in permanent problems such as a distorted pupil, alteration in the coloured part of the eye or even loss of vision.



Anaesthetic Risks

  • You will be given a separate information sheet regarding your anaesthetic by the anaesthetic department. Remember that anaesthetics are extremely safe but like any procedure there are small and potentially serious risks.  However, for a fit person undergoing routine surgery these are exceptionally small.  Unpredictable reactions occur in around one in 20,000 cases and unfortunately death in around one in 100,000.
  • Remember: these complications are detailed for your information and that the vast majority of people have no significant problems!


Frequently Asked Questions

Q: How long will I need to be off school/work?

A: Most people are able to return to their normal routine after three to four days so you should not need to be off for more than a week at most.

Q: How long before it is safe to go swimming?

A: We would normally advise that you allow the eye surface to heal over and wait 4 weeks before swimming.

Q: Are there any stitches to come out?

A: All the stitches we use will dissolve by themselves after the operation.

Q: Will I still need to patch/wear glasses after surgery?

A: Probably yes.  Surgery will not avoid the need for patching as although the eye may look straighter it may still be lazy.  Sometimes you may even need to start patching after surgery.  Also we usually aim to correct the size of squint present whilst wearing glasses.  This means that glasses are usually still needed after the operation and that you may still notice the eye turning when they are removed.


We hope you have found this advice helpful.  Please do not hesitate to contact us at our main Clinic or at our Spintex Road branch, with any queries or concerns you may have.


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