Adult squint is a misalignment of both eyes and effects about 4% of the adult population

The squint may be present all or only part of the time, in only one eye or alternating between the two eyes.

Adult squints are of three main types: non-paralytic, paralytic and restrictive.

  • Non-paralytic squints: They are usually a longstanding from childhood. The most common pattern is that an eye that was straight after childhood squint surgery later drifts out and causes concern over its appearance.
  • Paralytic squint: The eye does not move normally because one or more eye muscles are weak or paralysed. This problem may have developed as a result of other health problems, such as damage to cranial nerves, following head injury or as a complication of diabetes or stroke. Such people will, most likely, suffer from troublesome double vision.
  • Restrictive squint:  One or both eyes do not move fully because of scarring or tethering of one or more muscles.


Symptoms of adult squint problems include fatigue, double vision, difficulty with near vision and loss of stereo vision. To compensate for this, some individuals will adopt an abnormal head position. Many adults with squint are concerned about the appearance of their eyes and the impact this has on social relationships and work

This information aims to answer some of the questions you may have about squint surgery. However, it does not cover everything as every patient and squint is different. Your surgeon will discuss your particular case with you. Please ask the clinical staff about anything you want to be made clear.

What is the aim of surgery?

  • To improve the alignment of the eyes, to make the squint smaller in size.
  • In some patients, to reduce or try to eliminate double vision.
  • Occasionally to improve an abnormal position of the head.

How is the surgery done?

Squint surgery is a very common eye operation. It usually involves tightening or moving one or more of the outside eye muscles which move the eye. These muscles are attached quite close to the front of the eye under the conjunctiva, the clear surface layer. The eye is never taken out of the socket during surgery. Stitches are used to attach the muscles in their new positions.
Squint surgery is nearly always a day case procedure so you should be in and out of hospital on the same day.
There are two kinds of squint operation – adjustable and non-adjustable:

Non adjustable surgery

The operation is usually carried out under general anaesthetic. The operation usually takes up to 60 minutes depending on the number of muscles that need surgery. When you have recovered from the anaesthetic and the nurses are happy for you to be discharged, you are free to go home – usually a few hours later.

Adjustable surgery

Squint surgery using an adjustable suture may give a better result in certain types of squint e.g. patients who have had a squint operation before, patients with a squint due to injury or patients with thyroid eye problems.

Part 1 – The main operation

The main part of the operation is carried out in the operating theatre usually under general anaesthetic (with you asleep).

Part 2 – Adjusting the stitch

Once you have woken up from the anesthetic the final position of the muscles is adjusted when you are awake and able to look at a target. This is particularly useful for treating double vision. If you wear glasses for distance or near, these will need to be brought in with you for this part of the operation. Adjustment is usually done on the ward, after drops of anaesthetic have been put into the eye to take away any pain. You may however feel a pressure sensation.

Before the day of surgery

A pre-assessment is performed in the weeks leading up to the operation date.

What happens on the day of surgery?

You will be asked to come early so that you can be prepared for surgery. You should not drink or eat before the operation: the exact timings of this will be given before the day of the operation. Before being discharged after the operation, you will receive eye drops with instructions and a follow up appointment.

Does the surgery cure the squint?

Overall about 90% patients feel some improvement in their squint after surgery. The amount of correction that is right for one patient may be too much or too little for another with exactly the same size squint, so that the squint may not be completely corrected by the operation. Although the eyes may be straight just after surgery, many patients require more than one operation in their lifetime. If the squint returns it may drift in either the same or opposite direction. We can’t predict when that drift may occur.

What are the risks of the operation?

Squint surgery is generally a 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.

Under and overcorrection

As the results of squint surgery are not completely predictable, the original squint may still be present (undercorrection) or the squint direction may change over (overcorrection). Occasionally a different type of squint may occur. These problems may require another operation.

Double vision

You may experience double vision after surgery, as your brain adjusts to the new position of the eyes. This is common and often settles in days or weeks but may take months to improve. Some patients may continue to experience double vision when they look to the side in order to achieve a good effect when the eyes look straight ahead. Rarely, double vision whilst looking straight ahead can be permanent in which case further treatment might be needed. If you already experience double vision, you might experience a different type of double vision after surgery. Botulinum toxin injections are sometimes performed before surgery to assess your risk of this.


Some patients may have a mild allergic reaction to the medication they have been prescribed after surgery. This results in itching/irritation and some redness and puffiness of the eyelids. It usually settles very quickly when the drops are stopped. You may develop an infection or abscess around the stitches. This is more likely to occur if you go swimming within the first four weeks after surgery. A cyst can develop over the site of the stitches, which occasionally needs further surgery to remove it.


The redness in the eye can take as long as 3 months to go away. Occasionally the eye does not completely return to its normal colour, particularly with repeated operations.


Most of the scarring of the conjunctiva (skin of the eye) is not noticeable by three months, but occasionally visible scars will remain, especially with repeat operations.

Lost or slipped muscle

Rarely one of the eye muscles may slip back from its new position during the operation or shortly afterwards. If this occurs, the eye is less able to move around and, if severe, further surgery can be required. Sometimes it is not possible to correct this. The risk of slipped muscle requiring further surgery is about 1 in 1,000.

Needle penetration

If the stitches are too deep or the white of the eye is thin, a small hole in the eye may occur, which may require antibiotic treatment and possibly some laser treatment to seal the puncture site. Depending on the location of the hole, the sight may be affected. The risk of the needle passing too deeply is about 2%.

Anterior segment ischaemia

The blood circulation to the front of the eye can very rarely be reduced following surgery, producing a dilated pupil and blurred vision. This usually only occurs in patients who have had multiple surgeries. The risk is about 1 in 13,000 cases.


Infection is a rare complication but the risk  increases if drops are not instilled as directed and treatment not sought promptly. Significant infection is extremely rare but in the worst cases can cause loss of vision or the eye (endophthalmitis, orbital cellulitis).

Loss of vision

Although very rare, loss of vision in the eye being operated can occur from this surgery. Risk of serious damage to the eye or vision is approximately 1 in 30,000.

Anaesthetic risks

Anaesthetics are usually safe but there are small and potentially serious risks. Unpredictable reactions occur in around 1 in 20,000 cases and unfortunately death in around 1 in 100,000.
Remember: these complications are detailed for your information and that the vast majority of people have no significant problems. After the operation the eye(s) will be swollen, red and sore and the vision may be blurry. The eye may be quite painful.
Start the drops you have been prescribed that evening, and painkillers such as paracetamol and ibuprofen can be taken. The pain usually wears off within a few days. The redness and discomfort can last for up to 3 months particularly with adjustable and repeat squint operations.
You should not sign any legal documents or drive for 48 hours after the general anaesthetic.
We would advise that you may need one or occasionally two weeks off work. Work and normal activities including sport can be resumed as soon as you feel comfortable to do so. It is quite safe to use the eyes for visual tasks, for example reading, watching television. You should return for follow up as advised.

Summary of care after the operation

  • Use the eye drops
  • Use painkillers such as paracetamol and ibuprofen if the eyes are painful
  • Use cooled boiled water and a clean tissue or cotton wool to clean any stickiness of the eyes and avoid water entering the eyes from the bath or shower for the first two weeks
  • Don’t rub the eye(s) as this may loosen the stitches
  • No swimming for 4 weeks
  • Attend the postop clinic appointment
  • Continue using glasses if you have them
  • Avoid contact lens wear in the operated eye(s) until advised it is safe by the doctor or orthoptist

Adult Squint (Strabismus) Specialists


Dr. Suhair Twaij
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