How does surgery work?

The key to this question is to consider that we are dealing with defects in how the brain controls way the 2 eyes work together, not strengthening a "weak" muscle usually, nor weakening a strong one. The muscles themselves are normal, and our microsurgically is anatomically very precise.

Our surgery is forcing the brain to re-calibrate it's circuitry by mechanically aligning the eyes and giving it the chance to over-ride the faulty mechanisms that had been acting. 

How soon should you operate?

After 6 months of age, it is done as soon as both eyes have reasonable vision, and it is convenient for the family. The earlier surgery is done (usually from 6 months old) the more 'plastic' the brain's connections, the better the repair (this has been shown nicely in some scientific studies examining the outcomes of early and later surgery. 

Why does my child still need glasses after surgery?

A critical factor that determines why a child's eye becomes misaligned in the 1st place, and the response to surgery, is the effect of accomodation and the convergence reflex, and also clarity of vision.

The position, or "turn" of your eyes relative to each other is determined by a reflex that is at work to link your focusing effort to turning the eyes in. A child has little control over this reflex, but we can control it by giving them glasses. With the reflex more or less under control surgery can be embarked upon and give a predictable result. 

The aim of surgery is to give well aligned eyes, capable of working together with binocular vision and often stereo vision, and if the child needed glasses before the operation they will still be required afterwards (and some children are given glasses only after surgery). The force of the reflex declines with age, and so glasses may not always be needed, but to ensure good results of surgery you must always assume that your child should keep wearing them.

The amount of surgery done is matched to the maximum turn of the child's eyes while wearing their glasses before surgery. Thus after surgery the eyes should be well aligned with glasses on, but will often have a turn if they are off. For more about this see Accomodative esotropia.

Will they need more than 1 operation?

When a child's eyes are misaligned it means that the part of the brain responsible for getting them straight is abnormal. This abnormality is more profound in certain situations, such as when the eyes have been misaligned from very early in life, or when there are other neurological problems present.

80% of patients with Congenital esotropia (in-turned eyes) will require another operation at some stage in their lives. 20-33% of patients with later onset in- or out-turned eyes will need further operations after the 1st. Most of the reoperations occur in the 1st few years after the initial surgery.

The brain circuits may respond very well to surgery at first, with the 2 eyes working together. Often the eyes are not locked in this alignment, so that it can become necessary to reposition muscles again to keep the eyes within the range this circuitry can handle. 

Also, the eyes may be horizontally aligned, but because of the faulty control centres they may start drifting up or out, may turn in again, and sometimes turn out. This is recognised as a normal course for these patients, with careful attention to detail and fairly prompt intervention along the way they have a good chance of acheiving good, and sometimes completely normal vision, as well as excellent cosmesis.

Why are you operating on both eyes when only 1 is turning?

There are 3 general reasons why this can be the case:

1. After 100 years of surgery to correctly align eyes doctors have figured out that certain types of problems do better when certain operations are performed, and so the operation that gives the best outcome should be used.
2. The amount of misalignment, or features of the misalignment, mean that surgery on only 1 eye will not achieve the desired result. Operating on the other eye can increase the amount of turn that can be corrected, and can compensate for any unevenness between the eyes. An example is when the misalignment is so large that it could not be safely corrected by shifting the muscles in one eye alone, so 1 or 2 muscles in the other eye are operated on as well.                                 (Eye muscles can be shortened or weakened too much, with poor outcomes years later. The excessive moving or shortening of any one muscle must be avoided, which is possible by adding the effect of moving a muscle in the other eye).
3. Where a muscle has had previous surgery or has restricted or limited function, so that any further surgery will produce an unpredictable or very limited result.

The key is to realise that your 2 eyes move together as a single team, and they work to balance each other. Any alteration to one eye affects the other, and shifting the muscles of an eye which appears to be the "straight" one will allow the turned eye to move into it's correct alignment.

 

Is it safe to operate on the 'good' eye? (Risks of eye surgery)

When both eyes can see well then surgery on either or both eyes can produce the best outcome, regardless of which eye appears to be 'turned'.

When one eye has poor vision and the desired result can be achieved by surgery on one eye then it is always better to limit surgery to that eye.

This is because of the tiny risk that surgery could adversely affect the good eye's vision.

Put into context, the 1 in 20,000 risk of one eye losing vision after strabismus surgery = the risk each of us has of dying in an air travel accident.

Most people will fly many times in their life, very few patients ever need more than 2 or 3 operations to achieve well aligned eyes.

Sometimes the result of surgery will predictably be poor when only one eye is operated on. Things may intially appear much better, but it is quite common to find that the eye will turn back to almost as bad as it was before, sometimes over years. This also means that further surgery, ie on the good eye, becomes less likely to be effective. This is best avoided.