What is the aim of strabismus surgery?

To improve the alignment of your eyes, to make the squint smaller in size and/or in some patients to reduce or try to eliminate double vision.

How is the surgery done?

Squint surgery is a very common eye operation. It usually involves weakening or strengthening certain eye muscle(s) by moving the position of the eye muscle to give the desired effect.

The squint operation is usually performed on the squinting eye. In some cases, the operation has to be carried out on both eyes, and on occasions on the normal eye, usually if this is not a patient’s first squint operation. These muscles are attached 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 care procedure, and it is usually carried out under general anaesthetic, generally taking 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 within a few hours.

What will happen on the day?

When you arrive to the Mann Unit, situated on the first floor the Royal Free Hospital, the nurse will talk you through the process and take care of you throughout your day care stay.

The orthoptist will take some measurements and also ask you to complete a short questionnaire. The consultant ophthalmologist will go through the procedure with you and take your consent.

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. Common complications can be:

Under and overcorrection

As the results of squint surgery are not completely predictable, your original squint may still be present (under correction) or the squint direction may change (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 your eyes. This is common and often settles in a few days or weeks, but may take months to improve. Occasionally, further surgery is required for persistent double vision.


The redness in the eye can take as long as three months to go away. The eye may not completely return to its normal colour, particularly with repeated operations, but this is rare.


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


Infection is a risk with any operation and, although rare, can result in loss of vision. Using your eye drops post-operatively will minimise this risk.

Suture reaction

localised allergic reaction to the suture can occur. This can be remedied with minor surgery. The British Ophthalmic Surveillance Unit has conducted a study into severe complications of strabismus surgery in the UK.

These occur in three patients per 1000 (0.3 %) overall. These figures include:

  • Globe perforation: one patient in 1,000 (0.1%)
  • Muscle slippage: one patient in 1,100 (0.09%)
  • Loss of vision: one patient in 2,000 (0.05%)

After the operation

  • Your eye(s) will be swollen, red and sore and your vision may be blurry.
  • Use painkillers such as paracetamol and ibuprofen if your eyes are painful. The pain usually wears off within a few days.
  • Use your eye drops, which should be used for a period of two to four weeks.
  • It is important that you attend your post-operative (follow-up) clinic appointment.
  • Don’t rub your eye(s) as this may loosen the stitches.
  • Continue using glasses if you have any.
  • Use cooled boiled water and a clean tissue or gauze to clean any stickiness of your eyes and avoid water entering your eyes from the bath or shower for the first week.
  • Do not swim for four weeks.
  • Do not drive for 48 hours.
  • Avoid dusty, sandy atmospheres for two weeks after surgery.
  • Avoid wearing contact lens in the operated eye until you are advised it is safe by your doctor or orthoptist.

It usually takes a few weeks before the final outcome of the operation can be determined with certainty.

What should I do if I have concerns following the operation?

If you have any concerns in the first week after surgery, do not hesitate to call the hospital on 020 7794 0500 and ask to speak to the ophthalmologist on call or the ophthalmic nurse practitioner.

Please call if there is a yellow discharge from the eye or if the eye gets increasingly swollen and warm, or if the squint appears to be worse than prior to surgery.