Strabismus is misalignment of the eyes.
Causes include focusing (refractive) error and imbalance of muscles that control eye movement.
Symptoms include double vision and loss of vision.
The diagnosis is based on an eye examination.
Strabismus sometimes resolves on its own, but in most cases eyeglasses, contact lenses, or surgery is needed.
Strabismus occurs in about 3% of children. If left untreated, about 50% of children with strabismus have some vision loss due to amblyopia Amblyopia Amblyopia, a common cause of vision loss in children, is a decrease in vision that occurs because the brain ignores the image received from an eye. Vision loss may be permanent if the disorder... read more .
Causes of Strabismus
Strabismus may appear in the first few months of life or later in childhood, depending on the cause.
In children under 6 months of age, risk factors for strabismus include family history of strabismus, genetic disorders (such as Down syndrome Down Syndrome (Trisomy 21) Down syndrome is a chromosome disorder caused by an extra chromosome 21 that results in intellectual disability and physical abnormalities. Down syndrome is caused by an extra chromosome 21... read more ), prenatal drug exposure Drug Use During Pregnancy More than 50% of pregnant women take prescription or nonprescription (over-the-counter) drugs or use social drugs (such as tobacco and alcohol) or illicit drugs at some time during pregnancy... read more (including alcohol), prematurity Premature Newborn A premature newborn is a baby delivered before 37 weeks of gestation. Depending on when they are born, premature newborns have underdeveloped organs, which may not be ready to function outside... read more , birth defects of the eyes Eye Defects Eyes can be missing, deformed, or incompletely developed at birth. Birth defects, also called congenital anomalies, are physical abnormalities that occur before a baby is born. "Congenital"... read more , and cerebral palsy Cerebral Palsy (CP) Cerebral palsy refers to a group of symptoms that involve difficulty moving and muscle stiffness (spasticity). It results from brain malformations that occur before birth as the brain is developing... read more .
In children 6 months of age or older, strabismus is often caused by a refractive error Refractive Disorders in Children In refractive disorders, the eye is not able to properly focus images on the retina, causing blurred vision. Refractive disorders result in blurring of vision. Children may be unable to make... read more (excessive farsightedness [hyperopia]) or an imbalance in the pull of muscles that control the position of the eyes. Severe vision loss in one eye (due to refractive error or less common disorders such as cataracts) can cause strabismus because it interferes with the brain’s ability to maintain the alignment of the eyes. Other causes include retinoblastoma Retinoblastoma Retinoblastoma is a cancer of the retina, the light-sensing area at the back of the eye. Retinoblastomas result from a genetic mutation. The child may have a white pupil or cross-eyes or occasionally... read more (a type of eye cancer) and neurologic conditions such as cerebral palsy Cerebral Palsy (CP) Cerebral palsy refers to a group of symptoms that involve difficulty moving and muscle stiffness (spasticity). It results from brain malformations that occur before birth as the brain is developing... read more , spina bifida Spina bifida Neural tube defects are a certain type of birth defect of the brain, spine, and/or spinal cord. Neural tube defects can result in nerve damage, learning disabilities, paralysis, and death. The... read more , weakness of cranial nerves that control eye movement Third Cranial Nerve (Oculomotor Nerve) Palsy A palsy of the 3rd cranial nerve can impair eye movements, the response of pupils to light, or both. These palsies can occur when pressure is put on the nerve or the nerve does not get enough... read more , head injury Overview of Head Injuries Head injuries that involve the brain are particularly concerning. Common causes of head injuries include falls, motor vehicle crashes, assaults, and mishaps during sports and recreational activities... read more , and viral infection of the brain (encephalitis Viral Central Nervous System Infections in Children Central nervous system (brain and spinal cord) infections are extremely serious. Meningitis affects the membranes surrounding the brain and spinal cord. Encephalitis affects the brain itself... read more ). Sometimes a fracture of the eye socket Fractures of the Orbit A severe blow to the face can fracture any of several bones that form the orbit (the bony cavity that contains the eyeball, muscles, nerves, and blood vessels, as well as the structures that... read more can block movement of the eye and cause strabismus.
Types of Strabismus
There are several types of strabismus. Some types are characterized by inward turning of the eye (esotropia or cross-eye) and some by outward turning of the eye (exotropia or walleye). Other types are characterized by upward turning of the eye (hypertropia) or downward turning of the eye (hypotropia). The defect in alignment may be constant (the eye turns all of the time) or intermittent (the eye turns only some of the time) and may be mild or severe.
Strabismus: A Misaligned Eye
There are several types of strabismus. In the most common types, an eye turns inward (esotropia or cross-eye, top) or outward (exotropia or walleye, bottom). In this illustration, the child's right eye is affected.
A phoria is an unseen, minor misalignment of the eyes. This misalignment is easily corrected by the brain to maintain apparent alignment of the eyes and allow fusion of the images from both eyes. Thus, phorias usually do not cause symptoms and do not need treatment unless they are large and decompensate, causing double vision Vision, Double Double vision is seeing two images of one object. Double vision may occur when only one eye is open (monocular diplopia) or, more commonly, when both eyes are open (binocular diplopia). Binocular... read more (diplopia).
A tropia is a constant, visible deviation or misalignment of one eye or both eyes. An intermittent eye deviation that is frequent and poorly controlled by the brain is termed intermittent tropia.
Symptoms of Strabismus
Parents sometimes notice strabismus because the child squints or covers one eye. The defect may be detected by observing that the child's eyes appear to be positioned abnormally or do not move in unison.
Unless severe, phorias rarely cause symptoms. If they do cause symptoms, phorias typically cause eye strain.
Tropias sometimes cause symptoms. Younger children frequently lose vision in one eye (amblyopia) because their brain suppresses the image from the misaligned eye to avoid confusion and double vision. Older children may have double vision or they may have twisting or spasm of the neck (torticollis) to compensate for the misaligned eyes.
Diagnosis of Strabismus
Sometimes imaging tests
Children should be examined Preventive Health Care Visits in Infants Healthy infants should be seen by their doctor often during the first year of life. Preventive health care visits (also called well-child visits) typically take place within a few days after... read more periodically to measure vision and to detect strabismus starting at a few months of age. To examine an infant, a doctor shines a light into the eyes to see whether the light reflects back from the same location on each pupil.
Older children can be examined more thoroughly. Children may be asked to recognize objects or letters with one eye covered and to participate in tests to assess alignment of the eyes. All children with strabismus require examination by an eye doctor (ophthalmologist). (See also The Eye Examination The Eye Examination A person who has eye symptoms should be checked by a doctor. However, some eye disorders cause few or no symptoms in their early stages, so the eyes should be checked regularly (every 1 to 2... read more .)
Doctors may do imaging tests, such as computed tomography Computed Tomography (CT) In computed tomography (CT), which used to be called computed axial tomography (CAT), an x-ray source and x-ray detector rotate around a person. In modern scanners, the x-ray detector usually... read more (CT) or magnetic resonance imaging Magnetic Resonance Imaging (MRI) In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more (MRI), of the brain or spinal cord in children with cranial nerve palsies. In addition, blood tests may be done to look for genetic disorders.
Did You Know...
Prognosis for Strabismus
Strabismus should not be ignored or watched on the assumption that it will be outgrown. Permanent vision loss can occur if amblyopia occurs and is not treated promptly. Children treated at a later age can improve with treatment, but once the visual system has matured (typically by age 8), response to treatment is minimal. As a result, all children should have periodic formal vision screenings during the preschool years.
Success rates with surgical repair of strabismus can be greater than 80%. About 20% of children need another surgical procedure.
Treatment of Strabismus
Treatment of amblyopia if present
Eyeglasses or contact lenses
Surgery to align the eyes
If the defect is minor or intermittent, treatment may not be needed. However, if strabismus is severe or is progressing, treatment is required.
Treatment of strabismus depends on the characteristics and cause of the strabismus. Treatment is first aimed at equalizing vision (that is, correcting amblyopia Treatment Amblyopia, a common cause of vision loss in children, is a decrease in vision that occurs because the brain ignores the image received from an eye. Vision loss may be permanent if the disorder... read more ). Then, when vision is corrected as well as possible, doctors may do surgery to align the eyes.
Doctors equalize vision by forcing the child to use the weaker eye by putting a patch over the better eye (patching) or using eye drops to blur the vision in the better eye. Patching or using eye drops in the better eye allows the weaker eye to get stronger. Patching is not, however, a treatment for strabismus.
For children with significant refractive error Refractive Disorders in Children In refractive disorders, the eye is not able to properly focus images on the retina, causing blurred vision. Refractive disorders result in blurring of vision. Children may be unable to make... read more , doctors usually prescribe eyeglasses Eyeglasses Refractive errors can be corrected with glass or plastic lenses mounted in a frame (eyeglasses) or with a small lens made of plastic floating or resting on the cornea (contact lens). Good vision... read more or contact lenses Contact Lenses Refractive errors can be corrected with glass or plastic lenses mounted in a frame (eyeglasses) or with a small lens made of plastic floating or resting on the cornea (contact lens). Good vision... read more .
Sometimes eye exercises can help correct intermittent exotropia.
If these nonsurgical methods are unsuccessful in aligning the eyes satisfactorily, the eyes are aligned surgically. Surgical repair consists of loosening (recession) and tightening (resection) of the eye muscles. Children usually are not hospitalized for this surgical procedure. The procedure can cause complications, the most common of which are correction beyond what is needed (overcorrection) or correction below what is needed (undercorrection) and strabismus that returns later in life. Rarely, children may develop an infection, excessive bleeding, or vision loss.
The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
Children's Eye Foundation of AAPOS: Practical information about prevention, detection, research, and education to protect the vision of children