Exotropia: Types, Causes, and Management

Introduction

Exotropia is a form of strabismus in which there is a misalignment of the eyes. As a result, one or both eyes are outward turning. It can occur at any point in life. Exotropia can be congenital or acquired and constant or fixed. Acquired exotropia can be intermittent exotropia, sensory exotropia, and consecutive exotropia. The exacerbated angle of deviation is associated with tiredness, intake of alcohol, or any other sedatives. There is no racial predilection related to this disorder.

What Are the Types of Exotropia?

• Congenital Exotropia: Congenital form causes outward turning of the eyes since birth. It is a rare condition associated with craniofacial anomalies.

• Acquired Exotropia: Acquired Exotropia is acquired during a lifetime. It can be of the following types:

  • Intermittent Exotropia - Intermittent exotropia is a condition in which one eye is drifted or turned outwards. This is the most common type. Family members notice exotropia when the patient is tired or daydreaming or when the patient is looking at a distance. In some patients, it may progress, and the condition becomes constant. It affects females more as compared to males.

  • Sensory Exotropia - This is associated with poor vision and can occur at any age. Surgery is done to treat the permanent condition. Visual acuity is the primary cause of the misalignment of the eyes.

  • Consecutive Exotropia - This is seen following surgery to treat the crossed eyes and usually occurs because of overcorrection of defects.

What Are the Causes of Exotropia?

The exact etiology is unknown.

• Exotropia can be genetically acquired.

• Imbalance in muscles of the eyes.

• Cataracts (cloudy lens).

• Glaucoma (can cause vision loss and blindness by damaging the optic nerve).

• Stroke (occurs when blood supply to the part of the brain is reduced).

• Activities that tire the eyes can cause exotropia, such as watching television and playing games on a computer or using a computer for an extended period.

• Neurological disorders and alcohol abuse during pregnancy can increase the risk of exotropia.

• Genetic abnormalities can also lead to exotropia.

What Are the Symptoms Associated With Exotropia?

The following are the symptoms of exotropia:

• Unilateral or bilateral turning of eyes.

• Frequent rubbing of the eyes.

• Squints in the eyes can be observed because of sensitivity to light.

• Third cranial nerve palsy weakens the muscles of the eyes.

• Poor binocular vision (reduced vision in both eyes).

• Diplopia (double vision).

• Photosensitivity or increased sensitivity to light.

What Are the Complications Associated With Exotropia?

The complications associated with exotropia are the following:

• Headache.

• Problems in reading.

• Strain in eyes.

• The blurring of vision.

• The poor 3-dimensional vision of the patient.

• Amblyopia (lazy eye).

• Motion sickness.

• Outward turning of eyes.

How to Diagnose Exotropia?

• Vision Testing: Diagnosis is based on family history and testing of vision. An ophthalmologist and optometrist do vision testing. The doctor will ask one to read letters from the eye chart and place lenses in the eye to see how the eyes refract light. Dilating drops are also used to widen the eye's pupils to see the internal structure.

• Fundus Examination: A fundus examination is done to evaluate the retina.

• Cycloplegic Refraction: Cycloplegic refraction should be done every six months in patients with squints in the eyes.

• Cover Test: A cover test is done to check for the misalignment of eyes at a distance of 1/3 meter, six meters, and far distance.

• Binocular Single Vision (BSV): BSV should be checked for distance and near vision and repeated at each visit because it worsens with time.

• Prism Therapy: Prismotherapy promotes foveal stimulation, which means both eyes are directed at the same target.

• Slit-Lamp Examination: Slit lamp examination helps diagnose the condition and depicts the internal structure of the eyes. It helps evaluate the deformity in the retina, optic nerve, and blood vessels.

What Is the Treatment of Exotropia?

The treatment of exotropia is done to align the eyes and improve vision. Interprofessional team members are required to manage the disorder.

Non-Surgical Management:

1. Patient Counseling: Patients may need psychological assessment to deal with the social stigma associated with strabismus. Genetic consultations are essential because squints run in families.

2. Glasses: Glasses help in the treatment of misalignment of the eyes. They correct nearsightedness and farsightedness.

3. Exercise: Exercise may also help in the treatment of exotropia and also to improve focus.

4. Patching: Patching preserves binocular vision and helps treat the misalignment of the eyes.

5. Botulinum Toxin (Botox): Botox can be used to treat strabismus and eye malalignment and injected into the lateral rectus muscle.

6. Over-Minus Glasses: Using over-minus glasses may also help decrease the eye's misalignment.

7. Prism Therapy: Prism Therapy helps promote bi-foveal stimulation, which means both eyes are directed at the same target.

Surgical Management

Surgery is done to restore binocular vision and align the muscles. Surgery involves resection of extraocular muscles. Surgery is done under general anesthesia for a child, and local anesthesia is used for adults. The most common surgical procedures to cure exotropia include the following:

1. Bilateral lateral rectus recession.

2. Unilateral lateral rectus recession.

3. Medial rectus resection.

Surgery is the only option for patients with congenital exotropia to treat the disorder. Glasses may help to improve the refractive error and misalignment of the eyes. Complications of surgeries include slipped muscle, double vision, and scleral perforation.

What Is the Differential Diagnosis of Exotropia?

• Third nerve palsy (oculomotor nerve).

• Paralysis.

• Duane retraction syndrome (congenital strabismus).

• Crouzon syndrome (genetic syndrome where the skull is fused abnormally).

How to Prevent Exotropia?

While there is no surefire way to prevent exotropia, there are several steps that can help reduce the risk of developing this condition or worsening it:

• Regular Eye Exams: Regular eye exams can detect and treat vision problems early, preventing them from developing into more severe conditions like exotropia.

• Correct Vision Problems: If a person has any refractive errors such as nearsightedness, farsightedness, or astigmatism, they should wear corrective lenses or undergo refractive surgery to reduce the risk of developing exotropia.

• Eye Exercises: Eye exercises, such as those prescribed by a vision therapist or ophthalmologist, may help improve eye coordination and reduce the risk of developing exotropia.

• Early Intervention: If a child is diagnosed with exotropia or any other form of strabismus, early intervention with eye patching, eye drops, or surgery can prevent the condition from worsening.

• Avoiding Eye Strain: Spending long hours staring at a computer or phone screen, reading in poor lighting or other activities that cause eye strain may increase the risk of developing exotropia. Taking breaks, adjusting lighting, and practicing good eye habits can help reduce eye strain.

• Lifestyle Changes: Maintaining a healthy diet, getting regular exercise, and avoiding smoking can help reduce the risk of developing certain eye conditions, including exotropia.

Conclusion:

Exotropia is a common and curable condition. Early diagnosis helps in the intervention of the disorder. Multiple treatment options have been described above, and all have varying degrees of success. More advances in the field of diagnosis may help improve the treatment outcome. Follow-ups are required to ensure the disorder's condition and stage, correct usage of postoperative eye drops, and compliance with glasses as prescribed by the doctor.