Amblyopia, often called "lazy eye," is a condition in which poorer vision in one eye results in the brain favoring the stronger eye. The term "amblyopia" comes from the Greek word meaning "dull vision." Amblyopia is the leading cause of decreased vision in children, according to information released in 2008 from the Mayo Clinic. Amblyopia affects approximately 2 to 3 out of every 100 children, according to February 2010 data from the National Eye Institute.
Function
For a person to see an image clearly, both eyes have to focus on the image in the same place at the same time. In order to do this, the brain and eyes must work together. With amblyopia, one eye is able to focus more clearly than the other. The stronger eye takes over and the weaker eye sends blurry images to the brain, which it tends to ignore.
Features
Because the visual system develops between birth and age 7 to 9, early visual stimulation is important. The most common cause of amblyopia is strabismus, an imbalance in the muscles responsible for positioning of the eyes, which can cause the eyes to cross in or turn out, according to the Mayo Clinic. Strabismus is usually fairly easy to see. In other cases, one eye might simply wander slightly and not be so noticeable. Often the eye looks normal. Lack of depth perception is a feature of amblyopia that might alert a parent to a potential problem.
Diagnosis
The Mayo Clinic indicates that a thorough eye exam is sufficient to identify amblyopia and special diagnostic tests are not usually needed. The vision examinations should be a part of routine well-child visits. Diagnosis of infants and children to age three, depends on history of the infant's actions, observation and inspection of the eyes and eye lids, examining the pupil and the red reflex. Older children can participate in an examination using an age-appropriate eye chart. Routine vision screening in school may identify the child with amblyopia, but children may memorize the chart or "peek" to use the good eye for support. A difference of two lines of visual acuity is diagnostic of amblyopia. The vision in the amblyopic eye should be tested first.
Effects
If amblyopia is left untreated until age 9 or later, it may cause permanent vision impairment of the eye. The Mayo Clinic indicates this is the major cause of single-eye vision impairment in young and middle-aged adults. When treated early in children, vision generally improves in a matter of weeks to a few months. The goal is clear vision in both eyes.
Time Frame
The earlier amblyopia is diagnosed and treatment begun, the better. It is important for treatment to begin while the brain-eye connections are still developing. The U.S. Preventive Services Task Force (USPSTF) recommends vision screening on all well-child visits from newborn to five years. Children are often first identified with amblyopia during a preschool screening program.
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