Exotropia: Description, Causes and Risk Factors:Abbreviation: XT.Exotropia, commonly called wandering eye or wall-eye, is the visual condition in which a person uses only one eye to look at an object while the other eye turns outward. Exotropia is one of several types of strabismus, a condition resulting in eye turns or deviating eyes. This condition usually does not involve faulty or damaged eye muscles. Eye coordination may not be developed enough to provide normal control of the person's binocular vision.Pattern: A-pattern exotropia, V-pattern exotropia, X-pattern exotropia.Many people normally have a tendency for the eyes to drift outward when their eyes are completely relaxed, such as when they are “staring off into space” or while daydreaming. This outward drift, which occurs only in those moments of visual inattention, is called disease, and is controlled effortlessly when visual attention is refocused. Exotropia may occur rarely and result in few or no symptoms. However, in some people it may become more frequent or even progress to the point of becoming constant.Types: Exotropia may be congenital (present at birth) or acquired.Infantile Exotropia: A divergent strabismus that begins during the first 6 months of life is classified as infantile exotropia. It is less common than infantile esotropia. In infants, some cases of constant disease may be associated with neurological syndromes or defects, craniofacial syndromes, and structural abnormalities in the eye.An exotropia occurring after 6 months of age is considered to be acquired exotropia.Intermittent disease. In intermittent disease, the patient sometimes manifests diplopia, suppression, or anomalous retinal correspondence, and at other times, normal binocular alignment with good stereopsis. The period of strabismus and level of control are variable for each patient. Basic intermittent exotropia accounts for approximately 50 percent of all cases of intermittent the disease, with convergence insufficiency and divergence excess making up the balance of cases in approximately equal proportions. Intermittent disease typically presents between the ages of 1 and 4 years. In the United States, it occurs in approximately 1 percent of children by the age of 7 years. Without treatment over the years, intermittent the disease may either progress (both in degree and the amount of time it is manifest), stay the same, or, in some cases, improve. It rarely deteriorates to constant exotropia and fusion and some fixation at distance is usually maintained.
Acute disease. When a divergent strabismus develops suddenly in an older patient who previously had normal binocular vision, it is classified as acute exotropia. This condition can result from an underlying disease process or a decompensating disease.
Mechanical exotropia. Mechanical exotropia is a divergent strabismus caused by a mechanical restriction or tightness (e.g., fibrosis of muscle tissue, thyroid myopathy) or a physical obstruction of the extraocular muscles (orbital fracture), causing increasing exotropia. Tightness of the lateral rectus muscle may develop secondary to the primary innervational miswiring in a rare type of Duane syndrome. With this type of strabismus, an absence of adduction results in increasing disease accompanied by narrowing of the palpebral fissure and retraction of the globe.
Sensory disease. A divergent strabismus resulting from a unilateral decrease in vision that disrupts fusion, sensory disease may be due to a sensory deficit such as uncorrected anisometropia, unilateral cataract, or other unilateral visual impairment. Sensory exotropia and sensory esotropia occur with equal frequency in children under age 5; however, sensory disease predominates in persons older than 5 years. Sensory disease occurs in less than 3 percent of all strabismic children.
Consecutive exotropia. Exotropia that occurs following surgical or optical correction of an esotropia is referred to as consecutive disease. This form of a disease can also occur spontaneously in a formerly esotropic patient. A spontaneous change from esotropia to exotropia over time may be related to amblyopia of the deviating eye, weak binocular function, underaction of the medial rectus, or excessive hyperopic refractive error. When followed long term, the prevalence of consecutive disease is reported to be as high as 20 percent for esotropic patients treated with surgery.
The causes of disease are not fully understood. There are six muscles that control eye movement, four that move the eye up and down and two that move it side to side. All these muscles must be coordinated and working properly in order for the brain to see a single image. When one or more of these muscles doesn't work properly, some form of the disease may occur. Exotropia is more common in children with disorders that affect the brain such as cerebral palsy, Down syndrome, hydrocephalus, and brain tumors. One study has found that children with exotropia are three times more likely to develop a psychiatric disorder in comparison with the general population.Exotropia does run in families. All affected family members will not necessarily share exactly the same type of disease, meaning that disease may not be the only kind of misalignment possible. In some relatives, the exotropia may be obvious, while others may have a milder form. Many family members will not have disease at all. A family history of disease is a very good reason to have a child evaluated by a pediatric ophthalmologist.The patient with disease should be examined immediately, due to the possibility of an underlying disease process. Consultation with other health care professionals may be needed to determine the underlying cause of abducens nerve palsy, divergence paralysis/insufficiency, or acute acquired comitant esotropia, as well as acute exotropia in those cases in which the clinician is uncertain of the cause.Symptoms:People with disease may disease that outward drift only occasionally, such as when they are very tired, feeling sick, or after drinking alcohol, despite their efforts to refocus. Children may squint one eye in bright sunlight, or may rub one of their eyes. Their vision may become blurry or they may experience double vision when their eyes are misaligned. Some patients say that they can feel that an eye is misaligned, even though they do not see anything unusual. Others are unaware that an eye is turning unless it is mentioned by another person.Diagnosis:The ophthalmologist will perform all of the necessary tests to confirm that your child has an exotropia. The comprehensive strabismus examination should include the following elements:Assessment of fixation pattern and visual acuity in each eye.
Ocular alignment and motility at distance and near.
Extraocular muscle function (ductions and versions including incomitance, such as A and V patterns).
Detection of nystagmus.
Treatment:Eye muscle surgery to improve ocular alignment is generally recommended if one or more of the following criteria are present:If the exotropia is present for more than 50% of each day.
If the frequency of the exotropia is definitely increasing over time although it is not yet apparent for 50% of each day.
If there is a significant exotropia when your child intently views objects at near.
If there is evidence that your child is losing "binocular vision." This refers to the brain's ability to use both eyes together as a single unit. Among other benefits, binocular vision affords optimal depth perception.
If none of these criteria are met, surgical intervention is generally not recommended and simple observation with or without some form of eyeglass and/or patching therapy is then warranted.NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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