January 06, 2007

Lazy Eye (Amblyopia)


The brain and eyes work together to produce vision. If the brain favors one eye — usually due to poor vision in the other eye — the weaker eye tends to wander inward or outward. Eventually, the brain may ignore the signals received from the weaker eye. This condition is known as lazy eye (amblyopia).

Lazy eye is the leading cause of decreased vision among children. And lazy eye is fairly common. Lazy eye affects about two to three of every 100 children, according to the National Eye Institute.

Lazy eye is typically detected during childhood. Often, conservative treatments such as corrective eyewear or eye patches can correct lazy eye. In some cases, lazy eye requires surgical treatment. Left untreated, lazy eye may lead to permanent vision impairment.

Signs and symptoms
Lazy eye is characterized by an eye that wanders inward or outward. The eyes may not appear to work together. When the eyes aren't aligned, poor depth perception is likely as well.
Although lazy eye is most common in just one eye, it's possible for both eyes to be affected.

Anything that blurs a child's vision or causes the eyes to cross may cause lazy eye.
The most common culprit is strabismus — an imbalance in the muscles responsible for positioning of the eyes, which can cause the eyes to cross in or turn out. The muscle imbalance prevents the eyes from tracking with each other.

Sometimes lazy eye is the result of an anatomic or structural abnormality, such as an abnormal central retina or a cloudy area in the lens of the eye (cataract). In other cases, an abnormal eye shape or a size difference between the eyes contributes to lazy eye.
Occasionally, a wandering eye is the first sign of an eye tumor.

Risk factors
Lazy eye tends to run in families. Lazy eye may be more likely among children who were born prematurely or those who have developmental delays.

When to seek medical advice
Vision checks are often a routine part of well-child checkups — especially if there's a family history of crossed eyes, childhood cataracts or other eye conditions. For all children, a complete eye exam is usually recommended between ages 3 and 5. If you notice your child's eye wandering at any time beyond the first few weeks of life, consult your child's doctor for an evaluation. Depending on the circumstances, he or she may refer your child to a doctor who specializes in eye conditions (ophthalmologist).

Left untreated, lazy eye can cause permanent vision loss. In fact, lazy eye is the most common cause of single-eye vision impairment in young and middle-aged adults, according to the National Eye Institute.

Ideally, lazy eye treatment begins in early childhood — when the complicated connections between the eye and the brain are forming. Depending on the cause and the degree to which your child's vision is affected, treatment options may include:

Corrective eyewear. If a condition such as nearsightedness, farsightedness or astigmatism is contributing to lazy eye, corrective glasses or contact lenses will likely be prescribed. Sometimes corrective eyewear is all that's needed.

Eye patches. To stimulate the weaker eye, your child may wear an eye patch over the stronger eye — often for two or more hours a day. This helps the part of the brain that manages vision develop more completely.

Eyedrops. A daily or twice weekly drop of a drug called atropine can temporarily blur vision in the stronger eye. This will encourage use of the weaker eye.

Surgery. If your child has crossed or outwardly deviating eyes, the eye muscles may need surgical repair. Droopy eyelids or cataracts may also need surgical intervention.

For most children with lazy eye, proper treatment improves vision within weeks to several months — and the earlier treatment begins, the better. Although research suggests that the treatment window extends through at least age 17, results are better when treatment begins in early childhood.

Adapted from: Mayo Foundation for Medical Education and Research