Services for Children

Exotropia

Exotropia typically develops in a progressive course, as detailed below.

First, the eyes rarely turn outward, usually only when the patient is tired or sick.  As you know, when strabismus occurs with fatigue, or only under testing conditions, this is called an exophoria.

Next, the eyes start to spontaneously deviate outwards, and then straighten out moments later.  This is an intermittent exotropia.  When an intermittent tropia is present, it means that the brain is unable to keep the eyes aligned all of the time, but has the capability to keep them aligned some of the time. At this point, depth perception is still present but is at risk of being diminished or lost.

Finally, as the intermittent tropia becomes less controlled by the brain, the eyes will start to turn outwards more and more frequently – once the eyes are constantly turned outwards, this is an exotropia.

It is preferable to operate on an intermittent exotropia because we know that the binocular cells (in the brain) are still functioning and have the capacity to keep the eyes aligned at least some of the time. Once the eyes are constantly exotropic (always turned out), the binocular cells may be damaged to the point that binocularity has been lost – in this case, there is no stimulus for the eyes to remain straight.  

So, when is the best time to operate?  As an intermittent exotropia becomes more frequent.  The decision to operate is based on the frequency of the exo-deviation, not the size of the turn.   For example, a small constant exotropia can be operated on at any time, but a large intermittent exotropia that occurs infrequently is probably not ready for surgery.  

A few more things about exotropia:  First, people who are myopic (near-sighted) and have an exotropia should wear their glasses all of the time, because this can help to limit the frequency of the exotropia. Second, there is one form of exotropia where eye exercises can help – if the eyes turn out more when looking at something up close than when looking at something far away.  In this situation, which is called convergence insufficiency, specific eye muscle exercises can be effective if performed properly.  Convergence insufficiency is the only type of strabismus that has been shown to respond to eye movement exercises (orthoptics).