Exotropia is a less common form of strabismus.
As we have mentioned in previous chapters, the suffix (-tropia) indicates the marked presence of strabismus (in contrast with the suffix -phoria meaning the latent) and the prefix (exo) indicates the direction the eye with strabismus is facing.

One eye may only squint or sometimes one and sometimes the other.

It usually occurs between the ages of 2 and 5 years old. The first appearance of the exotropia occurs when the child is tired or sick and it only lasts for a few seconds until the child blinks his eyes or looks in another direction.

In its typical appearance, exotropia occurs when the child looks at an object at a distance farther than 3 meters. This makes it even more difficult for the parents to identify exotropia because they approach close to the child to observe his eyes, which in this case are aligned. However, over time the exotropia incidents are frequent and last longer.

It could be argued that since hyperopia causes esotropia, myopia may be the operative cause of exotropia. The real cause of exotropia remains unclear and children with exotropia have no refractive or other abnormality to an extent which differentiates them from children who don’t have strabismus.


Diplopia and repulsion

It’s more likely that children who have an eye that squints outwards also have a double vision. When this happens, they try to correct it by blinking (fast opening and closing of the eyelids) or by rubbing their eye. If they do not succeed, they are forced to close or cover with their hand the eye that squints to eliminate diplopia.

Such movements of the child are usually noticed outdoors, especially where there is a lot of sunlight or at home when the child is watching TV.

Gradually, the child's brain repels the image of the eye that squints, resulting in amblyopia. The vision’s impairment though is less important than the amblyopia caused by esotropia.


The treatment of exotropia

If amblyopia is coexisting, it must be treated before exotropia. This is achieved by covering the "good" eye, though sometimes, the ophthalmologist may recommend switching and covering one day the "good" eye and one day the weak one.

The definitive treatment of exotropia is by surgical correction.

Some ophthalmologists before resorting to surgery, try more conservative methods such as the use of myopic glasses, even if the child does not have myopia. The negative (myopic) lenses will help the child’s effort to adjust and the increased convergence that accompanies it may be enough to correct exotropia. In fact, the non-surgical methods are simply delaying surgery and sooner or later the child will have to undergo it, especially if exotropia has become permanent.


Convergence Insufficiency

The convergence insufficiency is a special form of exotropia that features the absence of strabismus at a distance vision and its transition to exotropia, only when the child focuses closely, eg when reading.

As its name indicates, this form of exotropia is due to the inability of the eyes to converge when looking closely. This results in prolonged copiopia occurring in nearby pursuits, such as reading. This problem usually occurs in adolescents or young adults, so it cannot be held responsible for learning difficulties in childhood.


Treatment of convergence insufficiency

The convergence insufficiency is mainly treated by orthoptist exercises that the patient could perform alone in his house. These are made using an object such as a pencil or a bulb, which the patient keeps in front of him with an outstretched hand and then moves it slowly towards his nose with his eyes focused on it.

So through continuous adaptation he essentially works the medial rectus muscles that are responsible for the convergence.

For an even more intense exercise program, prisms can be used, causing an even greater effort to converge an even better workout of the muscle.
The program with these exercises can last several months and if done properly, the symptoms of exotropia will improve.

With recurrence of the symptoms, the exercises are simply repeated. Surgical correction of the insufficient convergence is not generally appropriate.

In any case, any refractive error should be corrected, even hyperopia, that with its correction, we have decreasing of the adjustment.