Exotropia is a type of strabismus in which one or both eyes tend to deviate uncontrollably out of the face.
Exotropia, also known as divergent strabismus, differs from its opposite form, esotropia, where the eyes are directed towards the nose.
Diverging strabismus can occur at any age, usually between the ages of one to four years.
Early detection and treatment of the condition are important to improve vision and prevent subsequent complications.
Diverging strabismus can be classified according to the frequency with which the eye deviates:
- Intermittent: This type of divergent strabismus only occurs from time to time, may or may not be more frequent throughout the life of a person, this is the most common form of divergent strabismus.
- Constant: In this classification is located the divergent strabismus that presents symptoms where the eye remains in this position at all times.
According to the cause that causes it:
- Congenital: The divergent strabismus is present from birth, and is also known as divergent childish strabismus.
- Acquired: This condition is more common in women than in men and can be acquired in different ways.
Acquired forms of divergent strabismus include:
- Sensory divergent strabismus: It occurs when the eye presents problems of poor vision. This form of strabismus can be prevented and can easily be treated with the use of corrective eyeglasses.
- Mechanical divergent strabismus : Mechanical divergent strabismus is caused by a restriction or stiffness of the muscles that control the eye (fibrosis of the muscle tissue, thyroid myopathy) or a physical obstruction of the extraocular muscles (orbital fracture).
- Acute divergent strabismus: divergent strabismus that starts suddenly, usually occurs in older adults with an underlying disease process, such as problems in the cranial nerves or with thyroid disorders.
- Consecutive divergent strabismus: This occurs after the patient has undergone a strabismus corrective surgery (to correct the esotropia). Diverging strabismus may develop shortly after corrective surgery or may develop after several years.
Other types of divergent strabismus may include one with an excess of divergence and with a convergence insufficiency.
Causes of divergent strabismus
This condition may be related to some defects that involve the extraocular muscles, which are responsible for controlling the movement of the eyes.
Usually, these six muscles work together, when they send the signals to the brain and direct the eye movements so that both eyes can focus towards the same focal point.
When a difficulty arises and the muscles fail to work together, there is usually some type of strabismus, including divergent strabismus.
Other causes of divergent strabismus may involve nerves that are responsible for transmitting information to the brain or muscles, or those parts of the brain that direct these eye movements.
Eye injuries, such as suffering a traumatic brain injury, in addition to other circumstances associated with the health of the individual, may be the cause of the appearance of divergent strabismus.
Symptoms and signs
The first signs of divergent strabismus can be observed from childhood.
Most children who suffer from strabismus can not know they have a vision problem.
Normally, they believe that problems such as double vision or myopia are normal and do not express their inability to see clearly because they have never had a better vision.
Therefore, it is important that the signs and symptoms of these ocular conditions are detected, including divergent strabismus in time and to improve the quality of your vision.
- Excessive rubbing of the eyes due to the tension present in these.
- Cover or close an eye to improve vision.
- An increase in sensitivity to light or photophobia.
- Disorders in the direction of the gaze.
- Have a double vision.
- Blurry vision.
- Uncoordinated movements.
Intermittent divergent strabismus can be detected after six months of age, and is considered a progressive disorder that can be controlled at that stage and prevent it from becoming a constant divergent strabismus, if left untreated.
The first people to notice the presence of divergent strabismus in a child are the parents and the people who live with him.
When there are signs that warn divergent strabismus in babies, the ophthalmologist will place a light in the eyes to see if the light is reflected from the same point in each cornea.
In older children and adults, the eye exam is done more thoroughly.
Today there are several visual and ocular exams, which can help the specialist to establish what form of divergent strabismus the patient is presenting. These tests may include the following:
- Ocular motility tests: This test verifies the ability of the eye to move in all directions. The specialist will ask the patient to follow the finger while he draws an imaginary figure in the form of a double H that involves the eight fields of the gaze.
- The visual acuity test: This test measures the level at which the vision may be affected. In general, this is done by asking the patient to read the letters drawn on posters that are located far away and in the foreground. The normal acuity of distance vision is 20/20.
- Alignment: This test is performed to determine if the eyes are working in a coordinated manner. There are several methods that are used to verify the alignment of the eye.
- Refraction: This test determines the power that the lens must have for the adequate prescription of the formula that the patient needs to compensate for refractive errors, such as in the case of myopia, hyperopia or astigmatism .
A complete examination and evaluation of the eyes and vision are the most important steps in the diagnosis of this condition.
When necessary, a more detailed assessment of sensory, motor and refractive functions may be included.
The detailed history of the patient about the conditions of the onset of the condition, the frequency with which the deviation occurs, the family history that exists of strabismus.
As well as the presence of diplopia or any other problem related to vision, it will help the specialist to collect information about the general condition of the eye and make a good differential diagnosis.
Assessing the health of the eye would help detect congenital abnormalities and other coexisting conditions that may be causing divergent strabismus.
The visual acuity of each eye should be measured to verify the presence of amblyopia.
Visual acuity cards favor the quantification of the problem in children.
In the case of adults, psychometric acuity cards are recommended.
The unilateral test when the patient is fixed on an object, placing it far or near, helps to establish the frequency and extent of the deviation.
The test of the prism cover allows to assess the magnitude of the vision deviation.
For young children, the corneal reflex test is most often used .
As the refractive error is one of the most important causes to develop this condition, it must be measured accurately to decide the line of treatment.
And this measurement must be performed in conditions of paralysis of the ciliary muscle or not.
Neurological defects and the presence of craniofacial anomalies can be detected by imaging studies in the case of congenital divergent strabismus.
If there are other systemic abnormalities present, chromosomal studies may be suggested to verify the diagnosis.
The modality of therapy for the treatment of divergent strabismus, seeks to obtain a normal visual acuity in each eye, improving the alignment of the eye and improving the fusion.
The course of therapy will depend on factors such as the patient’s age at onset, the frequency and size of the deviation, or the presence or absence of amblyopia.
For patients who have good control of the deviation, any of the non-surgical measures can be used for optical correction.
This will also avoid the risk of surgical overcorrection.
The correction of refractive errors such as astigmatism and anisometropia will increase the fusion capacity and help improve divergent strabismus.
Negative lenses are useful to control divergence, especially in children of the age group of 2 to 17 years.
The progression of divergent strabismus can be limited by the patch of the eye, either dominant or alternate, depending on whether the condition is unilateral or bilateral. This helps prevent the deletion process.
The small deviations of the comitant strabismus can be controlled by base in prisms.
The point of close convergence is improved by convergence exercises, and this is particularly beneficial for patients with convergence insufficiency.
Botulinum toxin or botox injections are effective in treating secondary divergent strabismus.
In patients with bitemporal visual defects, prisms are recommended to avoid diplopia.
Surgery is suggested for those patients who have very poor control of the deviation and in those where the divergent strabismus is deteriorating.
Surgery is also recommended for those who have diplopia and severe muscular asthenopia.
The recession of the lateral rectus muscle, the resection of the ipsilateral internal rectus muscle and the resection of the bilateral medial rectus muscle are some of the surgical measures that are used to improve the different types of divergent strabismus.
There are many factors that your eye doctor takes into account when determining the appropriate method of treatment for your divergent strabismus:
- The magnitude of the exotropic deviation or how much the eye rotates outward.
- The frequency with which the deviation occurs.
- The age of the patient.
- The refractive error of the patient.
- The severity of the symptoms that the patient is experiencing.
In mild cases of divergent strabismus, corrective spectacles and vision therapy, such as eye exercises, are the most common treatment methods.
Eyeglasses are used to make each eye improve the quality of vision, to get both eyes to work together as a team.
Patients with convergence insufficiency may benefit more than those who suffer from other types of divergent strabismus.
The majority of patients with intermittent divergent strabismus, which is the most common form, can be instructed to recognize the condition and occasionally control the management of certain techniques that are shown during visual therapy.
Special glasses with prisms can be used to reduce double vision in patients with constant divergent strabismus.
In cases of moderate to severe children, the eye patch may be recommended.
In general, these eye patches are used for strabismic children who also suffer from amblyopia (decreased vision in one eye).
In the event that these methods fail, an eye muscle surgery can be performed. In general terms, it is not advisable to perform eye muscle surgery, it is only recommended in the following cases:
- Present divergent strabismus with a frequency greater than 50 percent each day.
- Present significant symptoms such as squinting, and eye strain, among others.
- Experience an increase in the frequency and duration of the episodes.
- Experience a significant divergent strabismus when looking at objects that are very close.
- When experiencing a decrease in binocular vision or depth perception.
During the procedure, the eye muscle is exposed by making a small incision in the tissue covering the eye.
The muscles of the eye are repositioned allowing the eye to move in the correct way.
This surgery is usually carried out with the patient under general anesthesia.
The total recovery usually takes around fifteen days.
After surgery, the specialist can indicate a treatment with analgesics for pain, antibiotics to combat and prevent the onset of infections and eye drops based on steroids, to reduce inflammation.
In general, any pain medication is used, with the exception of aspirin or similar products that can cause bleeding.
It is recommended that after the operation is performed:
- You should avoid getting your eyes wet until the specialist recommends it.
- Avoid exercising or swimming for a period determined by the doctor.
- You should wait a week to resume normal activities.
- Protective goggles should be worn, especially right after surgery, to compensate for sensitivity to light.
- Keep ophthalmic drops in the refrigerator, but do not freeze.
Untreated divergent strabismus can lead to permanent loss of vision in the form of amblyopia or permanent damage to the eye muscles.
Intermittent divergent strabismus can become a constant divergent strabismus, due to lack of treatment.
Sometimes, after having surgery, complications such as bleeding, infections of the surgical wound, swelling of the eyelid and the possibility of having to repeat surgeries may occur.
Since in certain occasions the divergent strabismus can reappear after the surgery.
You should go to the doctor immediately if symptoms and signs such as headache, dizziness, muscle aches, feeling of general malaise, fever, swelling, redness, if drainage or bleeding in the surgical area increases develop after surgery.
If new and unexplained symptoms appear, or if the medications taken after surgery cause unwanted side effects.
In the case of being detected and treated in time, it can restore the binocular vision of the patient.
Even if amblyopia develops, vision problems can be resolved during the early stages of disease progression.
The result of acquired divergent strabismus, on the other hand, depends on a wide variety of factors.
The surgical correction of misalignment at an early age, preferably before four years of age can help in the prevention of amblyopia.
But you must be very careful not to prescribe an excessive correction.
Surgery can also help increase functional control of vision muscles.
It is important to continue the treatment of refraction problems to obtain better results.
Postoperative care should include improvement of motor alignment and sensory functions to solve the problem completely.
Craniofacial syndromes can also be observed together with divergent strabismus in most cases.
After a period of time, this can become a fixation with one eye while the other eye develops amblyopia.
More than half of patients with congenital divergent strabismus can develop oblique muscle dysfunction.
When divergent strabismus is acquired, the patient may develop ocular fatigue after a prolonged session of visual work.
Some patients may develop diplopia. There are cases in which the patient tries to proactively control this deviation and feels that the objects seem closer and smaller.
Some patients, particularly children, tend to close one of the eyes with bright light.
It is considered that closing an eye helps to avoid diplopia and confusion in vision.
People with intermittent divergent strabismus may also complain of asthenopia, blurred vision, difficulty reading, and may have a headache.
When left untreated, intermittent divergent strabismus may deteriorate or remain the same over time.
Patients with consecutive divergent strabismus may suffer from a constant unilateral divergent strabismus while focusing on both distant and nearby objects.
They can also present high levels of stereopsis and the patient’s binocular vision capacity can be greatly reduced.
Diplopia is also a very common factor among these patients.
The divergent mechanical strabismus is characterized by a greater deviation of the axes of vision.
These patients tend to turn their heads as a compensatory habit to their visual problems.
Patients with divergent sensory strabismus may manifest high degrees of anisometropia and may also present vertical deviations very often in conjunction with outward gaze deviations.