Strabismus means that the eyes are not straight.  There many different types of strabismus, such as "crossed eyes" (esotropia), "wall-eyes" (exotropia), or "one eye higher than the other" (hypertropia).  These occur when eye muscles are too strong or weak.  There are 6 muscles that move each eye, so there are many combinations of weak or strong muscles that stop the eyes from being straight.  Surgery involves tightening weak eye muscles and loosening stronger muscles to balance their powers so that the eyes will point in the same direction and move together.  Stitches (sutures) are used to secure the muscles  in position onto the surface of the white coat of the eye (sclera).  Lasers are not used in this surgery and the eye is never removed from its socket.


Surgery is performed if all other treatments have failed to straighten the eyes.  These treatments can include glasses, prisms, eye exercises, or medications.  In some children patching is used to improve the vision in a "lazy eye" or to stop an eye turn from getting worse before surgery is done.


Surgery can be done using a general anaesthetic (patients is completely asleep) or using a local anaesthetic around the eye along with sedation.  In adults, some surgery can be done using an "adjustable" (or "movable") suture:  Instead of firmly tying the muscle stitches at the end of the surgery (as is usually done), they are left loose in a bow-tie knot.  After the anaesthetic wears off  and the patient is alert, the surgeon can measure the eye position.  If the eyes are not straight enough then the eye muscle can be moved to improve the result.  This  adjusting process is not painful since the eye is made numb by anaesthetic drops placed in the eye.


Eye muscle surgery is almost always done as an out-patient procedure.  In rare cases a patient has to be admitted to hospital on the day of surgery to be observed overnight.   If a patient has an adjustable suture operation, the adjusting of the eye muscle is done later on the same day.  Only rarely does a patient have to return to the hospital the next day to have the stitches adjusted.


Followup appointments after surgery are scheduled within the first week and at 6-8 weeks and 4-6 months.  The assessments at these appointments are as important as the surgery itself in leading to a successful result.   After surgery the eyes are red and slightly swollen over the muscles that were moved for up to 6 weeks.  The stitches dissolve on their own over 6 weeks.


Some patients have double vision ("seeing two of everything") right after eye muscle surgery because they are not used to the change in the position of their eyes.  Double vision goes away in over 90% of cases within the first 4 to 6 weeks after surgery as the patient gets used to the new direction of the eyes.  Other risks from the surgery include:


1. infections on the surface of the eye (risk 1 in 50) or inflammation from the stitches on the surface of the eye (risk 1 in 50)


2. infection in the eye socket (risk 1 in 500), damage to the eyeball from suture needles or the suture tracks (risk less than 1 in 1000), or infections within the eyeball (risk 1 in 30,000), and any of these three problems can lead to loss of vision in the eye


3. risks associated with general or local anaesthetics, which are uncommon


Overall, eye muscle surgery leads to straight eyes 80% of the time.  In other words, 1 in 5 patients needs further treatment or more surgery to get the eyes straight.