What is Exotropia?
Exotropia is a type of strabismus characterised by outward deviation of an eye. One of both eyes may be focused away from the eye under normal conditions. This may be noticed while looking at a distant object, a nearby object or while both. There are 2 types of exotropia:
- Constant Exotropia: This is when there is constant deviation of the eye.
- Intermittent Exotropia: This does not occur constantly. It occurs only once in a while. It is also known as alternating exotropia.
If Exotropia affects both eyes, as a result of which the individual is unable to align both eyes, the condition is termed as convergence insufficiency or exophoria.
Exotropia accounts for about 25 percent of malalignment of eyes in childhood. Transient intermittent exotropia may be seen within 4th to 6th weeks after birth but resolves by itself by the 6th to 8th week. In most of the cases, intermittent exotropia develops between the ages of 1- 4 years, which resolves by itself. However, if it does not resolve by itself, the condition will need medical attention. Symptoms of Exotropia usually start intermittently and gradually it becomes constant.
Symptoms of Exotropia
The most common symptoms of exotropia include:
- Outward deviation of the eyes
- Reduced depth perception
- Visual difficulties
- Photosensitivity or increased sensitivity to light.
Prognosis of Exotropia
Exotropia in childhood is often a self-limiting condition that resolves on its own. In adulthood, it does not correct by itself but can be reversed back to normal with surgical intervention. Surgical correction of exotropia has high success rate.
Causes of Exotropia
Exotropia may develop in childhood in view of poor vision in one eye. This is called as sensory exotropia. It is also seen in individuals with an existing family history of similar condition. Exotropia also presents itself in association with third cranial nerve palsy or past history of eye surgery particularly for strabismus. Childhood exotropia, if left untreated, can become constant exotropia in adulthood.
Risk Factors of Exotropia
The risk factors include:
- Genetic inheritance or positive family history of eye disorders
- Childhood cataract or glaucoma
- Untreated intermittent exotropia.
Complications of Exotropia
Untreated exotropia can cause permanent damage to eyes. Besides being anaesthetic, it can lead to partial or complete loss of vision. Complications also include amblyopia or damage to the eye muscles. Surgical correction may have complications such as uncontrolled bleeding, post-surgical infection, delayed healing, swelling etc.
Diagnosis of Exotropia
Diagnosis and treatment of exotropia is done by an orthoptist or an ophthalmologist. It is advised to visit an ophthalmologist as soon as the symptoms are noticed at their early stage. Besides a normal ophthalmological examination, there are some other investigatory studies that are done for diagnosis of exotropia. These include:
- Visual acuity test for each eye separately and both eyes together
- Cycloplegic refraction done after using dilating eye drops
- External exam or slit lamp exam
- Retinal examination or fundus examination
- Complete total eye examinations.
Treatment of Exotropia
In children with intermittent exotropia, that remains infrequent and under control, may not need any treatment. In such cases, watchful waiting by an experienced ophthalmologist is advised. In most of the cases the condition of exotropia is self-limiting and may resolve by itself. However, in some cases when the symptoms of exotropia are frequent and not under control, further treatment is recommended. In the initial stages correction with glasses, exercises and prisms are suggested but over the long run, this condition may require surgical correction. Surgery for exotropia is required to correct malalignment. The outcome of the surgery is more successful when done at a young age as it allows development of 3 dimensional vision or stereopsis. This also reduces risk of developing permanent vision loss from amblyopia.
The surgery for treating exotropia involves weakening of the lateral rectus muscle of the affected eye and strengthening of the medial rectus muscle as needed and based on the extent of the damage. It is performed by an eye surgeon or an optometrist in out-patient department. The patient recovers rapidly and can resume daily activities within a few days.
Exotropia is a type of strabismus characterised by deviation of the eyes away from the nose. The condition is either intermittent or constant. It usually occurs during childhood, which corrects by itself. However, it some cases, the condition does not improve and may need surgical correction. It is advised to get the surgical intervention done at an early stage to prevent further complications which includes permanent loss of vision.