Exotropia

Dr Ben Wild

Overview

Eye movements are controlled by 6 extra-ocular muscles. The superior rectus pulls the eye upwards, the inferior rectus pulls the eye downwards, the lateral rectus pulls the eye outwards and the medial rectus pulls the eye inwards. The superior oblique muscle connects to the eye after passing through a pulley called the trochlea and is mainly responsible for rotating the eye inwards and pushing the eye downwards. The inferior oblique follows a similar path as the superior oblique, except underneath the eye and does not travel through a pulley system.

A frontal image of a right eye with the extra-ocular muscles. If any of these muscles are too tight, too loose, too strong or too weak, there is the potential for an eye turn (strabismus).

Exotropia is a type of strabismus (eye turn) where one eye is seen wandering outwards compared to the other but all of the eye muscles still have full range of motion. There are a few different causes of exotropia that require different treatments.

Early onset exotropia often occurs at birth or soon afterwards and often presents alongside other neurological anomalies. Intermittent exotropia is the most common, is not always present, and can be caused by fatigue, ill health, bright light, and inattentiveness. Types of intermittent exotropia include convergence insufficiency, where one eye wanders outwards when looking at a near object, divergence excess, where one eye wanders when looking at a distant object and basic. Consecutive exotropia may occur after already having strabismus surgery.

A normal pair of eyes looking off into the distance.

An image showing the right eye is turned outwards. This is an exotropia style of strabismus.

Signs and Symptoms

Signs

One eye is turned outwards compared to the other. It may be constant or intermittent (comes and goes), it my be dependent on where the patient is looking, it may just be one eye or it may alternate eyes.

Symptoms

Usually no symptoms, possibly eye strain, possible double vision, lack of depth perception.

Causes and Risk Factors

Causes

Birth anomalies, vision impairment either in one or both eyes (cataract, retinal scarring, etc.), many still unknown factors.

Risk Factors

Family history of strabismus.

Prevention and Treatment

Prevention

1st eye exam around 1 year old followed by another at 3-4 years old to ensure proper development of the eyes and eye muscles.

Treatments

· Glasses or contacts after a cycloplegic refraction (prescription done after dilating drops).

· Treat any amblyopia (lazy eye) by patching the good eye 2hrs/day to full time.

· Treat any issues causing decreased vision.

· Vision therapy (eye exercises to regain proper eye muscle control).

· Surgery by age of 1 or 2 if born with strabismus or upon 1st discovering a strabismus is constant (doesn’t come and go).

Prognosis

If born with strabismus, surgery can align the eyes but the patient may need several re-alignment surgeries in their lifetime. There is also only a slim chance of gaining depth perception. If the strabismus develops after the age of 3-4, full glasses prescription and vision therapy can often correct the alignment issue, and if not, surgery can re-align the eyes. Regaining depth perception in this case is likely but not promised.