The Dr. Bill Takeshita Foundation

Last Modified: Sat, 18 Aug 2007

View other Common Causes of Vision Impairment

Strabismus is the medical term that describes the misalignment of one or both eyes. It is a relatively common condition that affects males and females equally and typically is present at birth or is observed during the first three years of life. Strabismus is more common among children who have eye pathology or medical conditions such as premature birth, retinopathy of prematurity, optic nerve hypoplasia, cortical vision impairment, cerebral palsy, Down’s syndrome, and developmental delay. However, strabismus is present among children with healthy eyes, especially those with a family history of strabismus, moderate to high degrees of hyperopia (farsightedness), and infants delivered using forceps. Children over the age of 3 years and adults can also develop strabismus as a result of trauma, stroke, cerebral vascular accident, brain tumors, and seizure disorders.

Strabismus may or may not cause problems for children born with this eye muscle coordination condition, may suffer from double vision, headaches, eye strain and sensitivity to glare and bright light. Conversely, some children will not have problems because their brain learns to adapt by only using one eye. Children and adults who develop strabismus after the age of 3 years almost always complain of double vision, headaches, poor depth perception, and have difficulty reading. Patients with strabismus will frequently turn or tilt their head, close or squint one eye, and cover one eye when reading or performing close work to eliminate double vision.

Strabismus is classified based on the direction that the eyes are misaligned, the frequency of the eye turn, and whether one or both eyes are involved. Divergent strabismus (exotropia) is when one or both eyes turn outward while convergent strabismus (esotropia) is when the eyes cross. Vertical strabismus (vertical tropia) is the term used to describe one eye pointing higher than the other. Strabismus may be constant or intermittent. Constant strabismus is when the eyes are always deviated while occasional misalignment of the eyes is called intermittent strabismus. Strabismus can affect one or both eyes and may be designated as unilateral, bilateral, or alternating strabismus. Unilateral is when only one eye turns. Patients with unilateral strabismus are at risk of developing strabismus amblyopia, a condition in which blurred sight cannot be corrected with glasses in the turned eye due to lack of stimulation to the brain. Bilateral strabismus is sometimes called alternating strabismus because the brain tends to take turns using the right and left eyes. Patients with alternating strabismus tend to not develop amblyopia because the brain cells are stimulated by both the right and left eyes.

There are many treatments available for strabismus. Eye muscle surgery is a surgical method to bring the eyes into proper alignment. The procedure typically involves the use of general anesthesia and the cutting of the eye muscles to reattach the muscles to straighten the eyes. Because it is not possible to ask infants if they see double, it is often necessary to perform additional eye muscle surgeries in the future. In some cases, vision therapy is recommended after eye muscle surgery to teach the brain how to coordinate the eyes together as a team, similar to the manner that physical therapy is recommended to patients after having orthopedic surgery.

Vision therapy is a program of exercises to teach the brain how to coordinate the eyes together as a team. It is provided by optometrists who specialize in binocular vision and involves the use of lenses, prisms, and filters to teach the brain how to coordinate the six muscles of each eye. Vision therapy is not a series of eye exercises but rather teaches children how to coordinate the various muscles together as a team. In many cases, vision therapy will also involve patching to treat patients with blurred sight due to strabismus amblyopia.

Glasses are frequently used to help patients with amblyopia. Many children born with high degrees of farsightedness have crossed eyes. The use of bifocal spectacles can often straighten the eyes without the need of surgery. The glasses allow the eye muscles to relax and thus straighten the eyes. Contact lenses and bifocals for reading are another method to correct crossed eyes due to farsightedness.

Children and adults who have double vision, headaches, and eyestrain may also benefit from the use of prismatic lenses and specialized glasses. Head trauma, cerebral vascular accidents, and strokes frequently cause very severe visual disturbances. The use of specialized glasses can eliminate symptoms of double vision, reduced depth perception, and dizziness.

Amblyopia is more common among children with strabismus. Amblyopia is the condition in which the visual centers of the brain do not receive maximal stimulation resulting in corrected sight with glasses that range from 20/40 to 20/200. Children with constant unilateral strabismus tend to develop amblyopia because the brain uses the vision of the straight eye and ignores the sight of the turned eye. Consequently, the visual cells of the brain that normally receive stimulation from the turned eye are not stimulated. Vision therapy patching is required to force the brain to use the crossed or turned eye to stimulate the brain cells.

Recommendations

• Take photographs of infant’s eyes at different times of the day. This will provide your eye doctor with photographs to assess the alignment of the eyes. Many children have a wide bridge, which creates the impression that the eyes are crossed when they are actually straight. Your doctor will look at the reflection of light on the cornea and determine whether the reflection is centered in each eye.
• All children should have their eyes examined by the age of 6 months. It is common for infants younger than 6 months to have problems coordinating their eyes as a team. By six months, the brain should be able to coordinate the eyes fairly well and by 12 months the eyes should not cross or turn.
• Children who require glasses should be prepared to wear glasses. Massage the face, ears, and regions of the head that will be in contact with the glasses. Perform these massage exercises during activities that the children enjoys, such as listening to soft music, taking a bath, or being put down for a nap.
• Children with strabismus will benefit from performing activities that will teach them to use the weaker eye. Shape sorters, puzzles, stringing beads, Lite Brite, and superimposing stickers are activities that can be performed with adult supervision to promote the development of sight in the weaker eye. See Developing Your Child’s Vision.
• Children with exotropia will benefit from the use of sunglasses or glasses that will turn into sunglasses when outdoors to reduce problems with glare. Most children with exotropia will tend to squint one eye when they are outdoors in the direct sunlight. In many cases, the eye will only turn when these children are outdoors in the bright light.
• Students with strabismus may have tracking eye movement problems that may cause them to lose their place when reading. Vision therapy activities can improve the tracking eye movement skills. For more information, see Vision and Learning.
• Students who complain of double vision, words moving while reading, or eyestrain when reading may be able to read more efficiently when they read with one eye. Experiment by asking such students to cover one eye and read. If their reading improves while reading with one eye, provide this information to the eye doctor and they may consider special glasses.
• Students and adults with double vision will benefit from prismatic glasses to eliminate the double vision. In some cases, patching or blurring of one eye can eliminate double vision while reading.
• Mild cases of strabismus can be treated with vision therapy activities. Many of these activities can be performed at home.
• For more information, please see Low Vision Rehabilitation