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What is amblyopia? | Types/causes | Diagnosis | Treatment | Role of the parent

What is amblyopia?

Amblyopia comes from Greek words "ambly" (dull) and "opia" (vision). Amblyopia is reduced or poor vision in an eye that didn't receive adequate use during early childhood and, as a result, didn't develop normal sight. It is sometimes called a "lazy eye."

Amblyopia is the most common eye problem in children. It affects two to three percent of the population, or about nine million people in the United States. Generally only one eye is affected. Amblyopia needs to be corrected during infancy or early childhood.

Newborns can see a little when they are first born, but their vision improves during the first few months of their life as they use their eyes. If they don't use an eye, their vision won't develop properly and may even decrease.

Visual brain cells develop during first decade of life. Any problem with a child's vision during that time can cause amblyopia. The problem must also be corrected during this time period. Once brain cells reach maturity, they can't be stimulated to develop properly if they haven't already developed. By age nine, a child's visual system is fully developed and can't be changed.

In amblyopia, the brain favors one eye over the other because one eye sends a clear message while the other eye sends a blurred message. The brain turns off the blurred message. The eye usually appears normal, but it is different in some way that causes the preference. Brain cells diminish in size when they aren't used, and vision doesn't develop in the eye.

People need to have good vision in both eyes. If a person has vision in only one eye and that eye is injured later in life, that person could be left without vision. Children should have their eyes checked by their pediatrician, family physician, or ophthalmologist by age four. If there is a problem, the child should be referred to an ophthalmologist. If there is a family history of misaligned eyes, the child should be checked before age three. If the cause of amblyopia is not corrected during early childhood and the weak eye is not stimulated, vision loss may be permanent.

Types/causes

Amblyopia can be caused by any condition that affects the normal use of the eyes and their visual development. Anything that prevents a clear image from being formed in one eye is a potential cause of amblyopia. Conditions associated with amblyopia may be inherited.

Strabismic amblyopia is the result of strabismus, or misaligned or "crossed" eyes. The misaligned eye "turns off." In other words, the brain learns to ignore the image from the deviated eye in order to avoid double vision, and the child uses only the "good eye."

Unequal focusing causes anisometropic amblyopia. Due to a refractive error, one eye is out of focus because it is more nearsighted, farsighted, or astigmatic than the other eye. The unfocused eye "turns off" and becomes amblyopic. This type of amblyopia is hard to detect. Both eyes can look normal, but one eye has poor vision. The eye professional must use a diagnostic eye exam to detect this condition.

Deprivation amblyopia is the result of deprivation of vision in one eye. The lack of vision may be from a congenital cataract, a tumor of the eye or eyelid, a disease of the retina or optic nerve, or cloudiness in eye tissue that is normally clear. Anything that prevents a clear image from being formed can cause amblyopia.

Diagnosis

Amblyopia is hard to diagnose unless one eye is obviously misaligned. The child's parent may not notice it, and the child may not be aware that he has one strong eye and one weak eye. Amblyopia is detected by finding a vision difference in the two eyes. In the very young child, the pediatrician will cover one eye and then have the child follow an object with the other. If one eye is amblyopic, the child may try to look around the patch, try to pull it off or cry.

If your child is experiencing some of the symptoms described here, it does not necessarily mean your child has amblyopia. However, if the child experiences one or more of these symptoms, you should contact your eye doctor for a complete exam. Click here for information on emergency or immediate care.

Treatment

Before the amblyopia can be treated, the eye professional must first treat the underlying condition that caused the amblyopia. The ophthalmologist may prescribe glasses to improve focusing or the misalignment of the eyes. If the eyes are misaligned, the ophthalmologist may do surgery on the eye muscles to straighten the eyes.

Treating the cause of amblyopia won't restore the child's vision, the weak eye has to be made stronger. To treat amblyopia, the child must be forced to use the weak eye. This is usually done by patching the strong eye for several weeks or months. Glasses may be needed to correct focusing problems. The ophthalmologist may blur the vision in the good eye with special eye drops or lenses to force child to use the amblyopic eye.

Usually, the younger the child is, the less time it takes to correct amblyopia. Regular eye examinations are a must to make sure amblyopia doesn't develop in the "good" eye.

If amblyopia isn't treated, several problems may occur. The amblyopic eye may develop a serious and permanent visual defect. In addition, depth perception (seeing in three dimensions) may be lost, and if the good eye becomes injured or diseased, the person may face a lifetime of poor vision.

The success for treating amblyopia depends on how severe it is and how early treatment is started. If amblyopia is detected early and treatment is started immediately, most of the vision can usually be restored. However, the child may need to continue treatment until around age nine. If the amblyopia is discovered after early childhood, treatment may not be as successful. Amblyopia due to strabismus or unequal refractive errors can be treated more successfully at a much older age than amblyopia caused by cloudy tissues.

Role of the parent

The parent has a very important role in treating and correcting amblyopia. Children don't like to have their eyes patched, particularly if they have been using the patched eye to see. They want to take the patch off and may be very uncooperative. The parents must convince the child that patching the eye is best for them. The parents must be very involved and must be able to gain the child's cooperation. The child will need lots of attention, hugging, and support until he or she gets used to the patch. Distraction works best for infants and toddlers. Bribery may also work well for toddlers. Reason generally works with older children.