Exotropia (Outward Eye Turn)

Eye-turns are interesting phenomenon that can occur at any stage of life and can go in different directions. Regardless of the deviation type it is important to have an assessment with a residency trained eye-care provider to determine the type and cause of eye-turn.

Some eye-turns can be associated with neurological conditions that can be life threatening, while others just need an appropriate pair of glasses. Quite frankly a strabismus (eye-turn) can be a daunting thing to assess for some providers because of the neurological involvement. That is why it is important to see a provider who is comfortable with working with a strabismus.
 

Here is a short summary of types of out-ward eye turns, also known as exotropias:

• Intermittent exotropia: An intermittent exotropia is when one eye remains fixated on a target while the other eye drifts outward some of the time. As you can assume from the name, this deviation is not constant. The frequency at which an intermittent exotropia can deviate can vary, making it difficult to catch in a vision screening in some cases. The magnitude of the deviation can also vary and may not be cosmetically noticable. Symptoms associated with an intermittent exotropia can be double vision, squinting in the bright sunlight, covering/closing an eye, blurry vision, poor reading fluency, etc.

• Alternating exotropia: An alternating exotropia is an outward eye turn that can alternate which eye deviates. Alternating exotropias can be constant or intermittent and can have varying magnitude (some are big and some are small). In some cases of constant alternating exotropia, the individual with the deviation, can switch focus between their eyes without changing the ocular posture. These people sometimes seem to have enhanced peripheral vision...depending on their ocular posture. Symptoms associated with an alternating exotropia can be the same as an intermittent exotropia but they may also be asymptomatic. For example, if the deviation is constant the brain has two options: See double or Suppress (ignore) the deviated eye to see singly. A chronic deviation is more likely to suppress than an acute deviation.

• Sensory Exotropia: A sensory exotropia is an outward deviation that occurs because of poor vision in the eye. In a perfect world each individual's eyes would see clearly and utilize the image from the macula. When an eye doesn't see clearly, for whatever reason (prescription vs health), the eye can begin to deviate because it is lacking a visual signal from the macula. These deviations can be more cosmetically noticeable. A surgery can be conducted to assist with cosmesis but the eye may drift back following the procedure because the lack of visual input may still be present.

•  

  : Cranial nerve III is a motor nerve that controls upper lid position, some eye movements, and pupillary responses. Cranial nerves originate in the brain and can travel through different cranial structures so when a cranial nerve palsy presents itself it is important to determine the causative factor. A third nerve palsy will most commonly present itself as an outward eye turn with an associated dilated pupil and a ptosis (upper lid droop). Pupils may not always be involved depending on the etiology. A third nerve palsy can be idiopathic but can also be acquired through trauma, vascular causes such as diabetes or high blood pressure, tumors, etc. A third nerve palsy should be thoroughly evaluated by a neuro-optometrist or a neuro-ophthalmologist. Certain causes such as an aneurysm can have serious health implications.Cranial Third Nerve Palsy

Treatment options for exotropia are not always the same. There are a variety of treatments for exotropia that include surgical correction, vision therapy, prism, or corrective lenses. It is important to recognize that not all treatments are curing an exotropia. Generally an individual with an exotropia will have a residual deviation but they may have greater control of the deviation in all cases of treatment. Exotropias may also spontaneously resolve, depending on the etiology, or decrease in frequency or magnitude. It is also important to note that an exotropia can occur at any age and proper evaluation is indicated because not all eye-turns are constant, not all eye-turns are cosmetically noticeable, and an exotropia may indicate other health complications.

Of course there are people who will have a higher risk of having an exotropia, most commonly is if a family member has an eye-turn of any type. If a parent or a sibling has an eye-turn, a comprehensive eye examination is recommended for every family member. This eye examination should be performed by an eye-care provider with residency-training in pediatrics or binocular vision/neuro-optometry. Keep in mind that a vision screening is not an adequate replacement of a comprehensive examination or assessment of an individual's ocular posture.

An exotropia is an outward eye turn that can have a large variety of presentations. It can be intermittent, constant, unilateral, alternating and vary in magnitude. An exotropia has a variety of causes, some of which can be life threatening. If an eye-turn is suspected or there is a family history of an eye-turn a comprehensive eye-examination is indicated.