Article updated and reviewed by Raymond S. Douglas, M.D., Ph.D., Assistant Clinical Professor Ophthalmology, UCLA School of Medicine/Jules Stein Eye Institute/UCLA & Director, Orbital and Ophthalmic Plastic and Reconstructive Surgery, Greater Los Angeles Veterans Administration Hospital . Editorial review provided by VeriMed Healthcare Network on May 2, 2005.
Strabismus is a visual defect in which the eyes are misaligned and point in different directions. Strabismus can occur early in childhood or later in adulthood, although the causes of the eye misalignment are different. Strabismus can be the first sign of a serious vision problem
With normal binocular (two-eyed) vision, both eyes are aimed at the same target. The visual portion of the brain fuses the two pictures into a single 3-dimensional image.
When one eye is misaligned, as in strabismus, two different pictures are sent to the brain. When misalignment occurs in childhood the consequences can be severe. If the eyes are misaligned, two different views of the world are sent to the brain. The brain often responds by ignoring one of the images. When the brain ignores an image in early childhood, development of vision is limited. The end result if left untreated can be amblyopia or decreased vision with loss of binocularity (depth perception).
Prevention of vision loss associated with strabismus is critical. Early vision screening starting at 6 months of age is becoming increasingly common among pediatricians. Vision screening in children is also becoming easier with the development of vision screening tests which measure brain waves in response to objects. These newer techniques allow vision screening in very young children in a pediatric office which is painless and quick. Again, the major consequence of strabismus in young children is permanent vision loss, so children should undergo vision screening and at the first indication of eye misalignment call your pediatrician.
Adults who develop strabismus often have double vision because the brain is already trained to receive images from both eyes and cannot ignore the image from the turned eye. The causes of adult strabismus are different from childhood strabismus.
The misalignment in children and adults may be always noticeable, or it may come and go. One eye may be directed straight ahead, while the other eye is turned inward, outward, upward or downward. The turned eye may straighten at times and the straight eye may turn.
The two most common types of strabismus are esotropia and exotropia.
Esotropia describes an inward turning eye and is the most common type of strabismus in infants. Young children with esotropia do not use their eyes together and the risk of amblyopia or poor vision development is the major concern.
Exotropia, or an outward turning eye, is another common type. This occurs most often when a child is focusing on distant objects. Typically, exotropia has less severe consequences upon visual development. Both forms can typically be corrected medically or surgically.
Strabismus is a common condition among children, but can also occur later in life. It occurs equally in males and females and may run in families. However, many people with strabismus have no relatives with the problem.
The exact cause of the misalignment is not fully understood. Six eye muscles, controlling eye movements, are attached to the outside of each eye. In each eye, two muscles move the eye right and left. The other four muscles move it up or down and control tilting movements. To line up and focus both eyes on a single target, all eye muscles of each eye must be balanced and working together with the corresponding muscles of the opposite eye.
In children, eye misalignment is an urgent condition and needs prompt evaluation by an ophthalmologist. The misalignment can be due to a variety of causes including maldevelopment of the eye or even tumors. More commonly the misalignment can be related to the need for glasses. In fact, glasses are an important treatment for strabismus in children. Thus routine vision screening with a pediatrician can often prevent the development of some forms of strabismus.
Most importantly, the treatment for strabismus MUST include evaluation and treatment for vision loss or amblyopia. If abnormal visual development is recognized early, many of the consequences of amblyopia can be reversed or prevented. Treatment for amblyopia can include glasses, eye patching or eye drops.
The brain controls the eye muscles, which explains why children with disorders that affect the brain, such as cerebral palsy, Down's syndrome, and brain tumors often have strabismus.
Causes in adults can be quite varied and also require prompt medical attention. Double vision or strabismus can be the first sign of a serious medical condition including stroke, or brain injury.
The primary sign of strabismus is an eye that is not directed straight. Sometimes a youngster will squint with one eye in bright sunlight. Symptoms of faulty depth perception may also be noticed.
Adults who acquire strabismus will usually have double vision.
Your physician will take a complete medical history and perform a physical examination including an eye exam.
Treatment goals for strabismus are to preserve vision, to straighten the eyes, and to restore binocular vision. Depending on the cause of the strabismus, treatment may involve repositioning the unbalanced eye muscles, removing a cataract, or correcting other conditions which are causing the eyes to turn.
Strabismus surgery involves making a small incision in the tissue covering the eye which allows the ophthalmologist (eye doctor) access to the underlying eye muscles. Which eye muscles are repositioned depends on the direction the eye is turning. It may be necessary to perform surgery on both eyes.
When strabismus surgery is performed on children, a general anesthetic is required. Local anesthesia is an option for adults. Recovery time is rapid and people are usually able to resume their normal activities in a few days.
Early surgery is recommended to correct strabismus because younger infants can develop normal sight and binocular vision once the eyes are straightened.
Amblyopia treatment is aimed at the underlying cause but may include glasses, eye patching or eye drops.
Strabismus treatment in adults also can vary. Occasionally strabismus can resolve spontaneously – but still requires urgent medical evaluation. Strabismus surgery in adults often includes use of adjustable sutures which can “fine tune” eye alignment shortly after surgery or the next day.
Is there a misalignment of the eyes?
What is the cause of the misalignment?
Is it esotropia or exotropia?
Is there a problem with vision in the eye(s)?
Is surgery required to correct the problem?
How will this be performed?
Will the surgery completely correct the problem?