Lazy eye (amblyopia) is decreased vision that results from abnormal visual development in infancy and early childhood. Although lazy eye usually affects only one eye, it can affect both eyes. Lazy eye is the leading cause of decreased vision among children. Left untreated, vision loss may range from mild to severe.

With lazy eye, there may not be an obvious abnormality of the eye. Lazy eye develops when nerve pathways between the brain and the eye aren't properly stimulated. As a result, the brain favors one eye, usually due to poor vision in the other eye. The weaker eye tends to wander. Eventually, the brain may ignore the signals received from the weaker — or lazy — eye.

Usually doctors can correct lazy eye with eye patches, eyedrops, and glasses or contact lenses. Sometimes lazy eye requires surgical treatment.

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Signs and symptoms of lazy eye include:

• An eye that wanders inward or outward
• Eyes that may not appear to work together
• Poor depth perception

Although lazy eye usually affects just one eye, it's possible for both eyes to be affected. Sometimes lazy eye is not evident without an eye exam.

When to see a doctor

Primary care doctors often check vision as a routine part of well-child checkups — especially if there's a family history of crossed eyes, childhood cataracts or other eye conditions. If you notice your child's eye wandering at any time beyond the first few weeks of life, consult your child's doctor.

Depending on the circumstances, your doctor may refer your child to a specialist in eye conditions (ophthalmologist or optometrist). For all children, a complete eye exam is recommended between ages 3 and 5.

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Anything that blurs a child's vision or causes the eyes to cross or turn out may cause lazy eye. There are three common causes of lazy eye:

• Strabismic. The most common cause of lazy eye is strabismus — an imbalance in the muscles responsible for positioning of the eyes. This imbalance can cause the eyes to cross in or turn out. The muscle imbalance prevents the eyes from tracking together in a coordinated way.
• Deprivation. Deprivation lazy eye occurs if there is a problem with one eye, such as a cloudy area in the lens (cataract). This "deprives" the child of clear vision in the eye.
• Refractive. This type of lazy eye is the result of a significant difference between the vision in each eye, due to nearsightedness, farsightedness or an imperfection on the surface of the eye (astigmatism). These are the types of vision problems typically corrected by glasses or contact lenses.

Occasionally, a wandering eye is the first sign of an eye tumor.

Source: http://www.mayoclinic.com

Your doctor will diagnose lazy eye with a thorough eye exam. He or she will look for a wandering eye, as well as a difference in vision between the eyes or poor vision in both eyes. Depending on your child's age, tests may include the following:

• Newborns. Red reflex test to look for cataracts, using a lighted magnifying device (ophthalmoscope)
• Infants. Test for ability to fixate their gaze and follow a moving object, as well as check for strabismus
• Toddlers. Red reflex test, photo screening or remote autorefraction
• Preschoolers and older children. Testing using pictures or letters. Each eye is patched in turn to test the other

Your doctor may also check for inflammation, tumors and other inner eye problems.

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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.

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Lazy eye tends to run in families. Lazy eye may be more likely among children who are born prematurely or with low birth weight, or who are born in a family with a history of childhood cataracts or serious eye disease.

Source: http://www.mayoclinic.com