The eyes are not properly aligned and do not focus on an object together at the same time. One eye may be turned all of the time or only some of the time. Most people who have strabismus are usually born with it or develop it at an early age. However, some forms of strabismus occur later in life.
Symptoms:
Newborns often have crossed eyes to some degree due to underdeveloped vision, but this usually disappears by the age of 3 to 4 months. True strabismus does not disappear as the child grows. If you think your child is showing signs of true strabismus, it is important to seek the advice of an eye care professional. The earlier the detection and treatment, the better the child's vision will be. Symptoms to watch out for include:
- Eyes that appear crossed
- Eyes that do not align in the same direction
- Eyes that do not move together
- Double vision
- Vision in only one eye, with loss of depth perception
Causes:
Strabismus is caused by a weak eye muscle or a weak signal from the nerve that controls the eye muscle. Frequently, uncorrected farsightedness and focusing problems are the underlying causes of strabismus in children. Some children are born with a defective visual processing center in the brain. Strabismus may also develop if a child is born with a cataract. It is common in conditions such as Down’s syndrome and cerebral palsy. Bleeding in the brain, a brain tumor, nervous system disorders, diabetes, high blood pressure, myasthenia gravis, thyroid disease and severe vision loss can also cause strabismus.
Risk factors:
One of the highest risk factors for strabismus is having a family history of strabismus. Having a moderate to high amount of farsightedness at a young age can also increase the risk significantly, as does having a disease such as diabetes or high blood pressure. In addition, strabismus may develop as a complication of any other disease causing vision loss.
Types:
Strabismus is categorized as being either constant (turned in all of the time) or intermittent (turned in some of the time). Cases of crossed-eyes, or esotropia, are classified as either "congenital" or "accommodative" esotropia.
- Congenital esotropia: An uncommon condition in which a baby is born with an inward turn of a large amount, usually appearing between the ages of 2 and 4 months.
- Accommodative esotropia: An inward turning eye that occurs because the eye is attempting to compensate for uncorrected farsightedness or a focusing disorder.
Diagnosis:
Besides parents, a pediatrician or family doctor is often the first person to detect strabismus. A baby whose eyes do not appear straight by the age of 3 to 4 months should be examined. To properly diagnose strabismus, a complete eye examination must be performed by an eye doctor. Early diagnosis is very important, as some eye turns may be a result of a serious medical condition. Strabismus that is not treated early in a child’s life may cause amblyopia (lazy eye), a condition in which vision develops poorly. In addition, the cosmetic appearance of strabismus may cause a lack of self-esteem.
Treatment:
Strabismus cannot be outgrown. Treatment to straighten the eyes is required. Treatment will depend on the type of strabismus and its cause:
- Glasses may be prescribed to improve focusing and enable the eyes to straighten.
- Patching the good eye will force a patient to use the affected eye. Patching will improve the chances of normal vision to develop.
- Eye drops may be used to blur the good eye, forcing the affected eye to be used. (This achieves the same result as patching.)
- Eye muscle surgery may be an option if non-surgical treatments do not work.
- Some eye doctors may prescribe eye exercises before or after surgery.
When to call the eye doctor:
Make an appointment with your eye doctor if your child shows signs of any of the following:
- double vision
- cross-eyed appearance
- poor vision
- eyes that do not fixate on the same point
Source:
Caloroso, Elizabeth, and Michael Rouse. Clinical Management of Strabismus. Newton, MA: Butterworth-Heinmann, 1993.
