Commonly presenting as misaligned or crossed eyes, strabismus most frequently presents in childhood, although many adults are faced with this ocular problem. The Neuro-ophthalmology Service at Scheie Eye Institute are experts at treating adult strabismus. Penn pediatric ophthalmologists at Children’s Hospital of Philadelphia combine the expertise of ophthalmology, neurology and pediatric ophthalmology to treat strabismus in children. To refer a child for treatment, call (215)590-2791 for an appointment in Pediatric Ophthalmology.
What is Strabismus?
Strabismus is the medical term for misaligned eyes. The eyes may turn inward (cross or esotropia), outward (splayed or exotropia), or be vertically misaligned (hypertropia). One eye looks forward while the other turns inward, outward, upward or downward. In addition, each eye may alternate between looking straight ahead and turning. As a result, your eyes do not work together. Each sees a different image, rather than the normal single fused image.
Strabismus can occur at anytime - infancy, early childhood, or adulthood. When it happens in children, double vision rarely results because the brain is able to process the image from one eye while suppressing the vision in the other. However, when strabismus presents in adults, double vision may occur. In some adults, a childhood misalignment may worsen and double vision may or may not be present.
Some lay individuals use the term ”lazy eye” to refer to strabismus, but this latter term is also used to refer to amblyopia (a condition in which an eye does not develop vision normally). Strabismus occurs in 3-5% of the population.
Causes of Strabismus
The following are the most common causes of strabismus in adults:
- Childhood history of strabismus (with or without previous surgery)
- Orbital disease such as thyroid eye disease
- Previous stroke or previous neurosurgical procedure
- Head trauma
- Diseases that affect the nerves, such as multiple sclerosis
- Poor vision in one eye
Symptoms of Strabismus
A person with strabismus may or may not experience double vision (diplopia). Whether or not a person develops diplopia depends upon the age of onset of the strabismus. Younger children below the ages of 6 to 7 will not usually develop double vision even though their eyes are not aligned, although they may be seen to be squinting. The brain of a child has a unique capacity to suppress the image in one eye; in essence, the child is only looking out of one eye at any given time. If one eye is always favored, which is frequently the case, the other unused eye may develop a condition known as strabismic amblyopia.
The capacity for the brain to suppress the vision in one eye is actually maintained throughout life. Consequently, however, people who suppress the vision in one eye do not develop true depth perception (stereopis). Most people function well in life without depth perception because they learn to use other visual cues to compensate for their lack of stereopsis.
The main symptom is a turned eye, although significant misalignment may be present without a visible difference in the position of the two eyes. However, adults frequently experience double vision. Other patients may experience symptoms that may seem vague including trouble focusing, eyestrain, images jumping, difficulty tracking on a page, or loss of peripheral vision.
Treatment of Strabismus
The primary goal is to align the eyes and restore binocular vision. Only after a complete eye examination can your ophthalmologist suggest the appropriate optical, medical or surgical therapy. Treatment depends on the type of strabismus.
Non-surgical Treatment of Strabismus
Standard eyeglasses can correct some forms of strabismus. Spectacles with prisms may also be useful in certain types of strabismus, particularly adults. Note, however, that the use of prisms in some types of strabismus is controversial. In patients with small angle deviations, prisms (eyeglass lenses that shift the image from one eye toward the other) can be either temporary (paste on) or actually ground into the patient's eyeglass lens. Prisms in glasses rarely can make the alignment worse over time. Eye exercises are also controversial. Eye exercises are probably helpful for a condition known as convergence insufficiency, but not most forms of strabismus. There are no medications available to treat most forms of strabismus.
Surgical Treatment of Strabismus
If glasses do not correct the misalignment, surgery may be successful. The eyes are straightened surgically by shortening or lengthening the muscles that control eye movement. Six different muscles operating in different vectors control each eye, and each muscle in one eye is paired with a muscle from the other eye. Surgery frequently involves both eyes; that is, the paired muscles are moved appropriately in each eye. Strabismus surgery has few serious complications, except that the eyes may still not be aligned after surgery in a small number of patients. Rare complications include bleeding, perforation of the eye, infection, retinal detachment, and diplopia.
Your surgeon may choose to use an adjustable suture. In this procedure, the operation is done to place one or more muscles on a pulley. The pulleys are then adjusted the next day with the patient awake thereby increasing the likelihood of successful alignment of the eyes. There is only minimal discomfort involved with this adjustment procedure.
People recover quickly from this procedure and are able to return to normal activities within a few days. In a few instances, additional surgery may be necessary to keep the eyes aligned. Strabismus surgery is usually a safe and effective treatment.