What Is Amblyopia?
According to the National Eye Institute, amblyopia is the most common cause of visual impairment in children – affecting 2-3 children out of every 100. If not treated, it is likely to continue into adulthood. The best time to correct amblyopia is during infancy or early childhood.
Our eyes and brains must work together for us to see properly. The reduced vision that results in one eye, when the brain and eye aren’t working in sync, is called amblyopia. Although the eye appears normal, it isn’t working as it should, usually because of an eye turn (strabismus) or a refractive error (nearsighted, farsighted, astigmatism). When one eye sees clearly and the other eye sees a blur, the brain suppresses or “turns off” the image from the blurry eye.
This condition is sometimes called “lazy eye" and normally occurs in only one eye, but it can occur in both. The vision reduction that is caused by amblyopia cannot be corrected with eyeglasses. Since the vision system normally is fully developed by age 9, it is important to identify and treat the problem early. The development of equal vision in both eyes is essential for you to have normal binocular vision, and good depth perception.
Amblyopia has three major causes:
- Strabimus (misaligned or crossed eyes): If someone has strabismus, he or she uses only the "good" eye. The brain effectively tunes out the "bad" eye to avoid double vision. Amblyopia occurs as a result of a constant misalignment in one eye.
- Unequal focus / refractive error: This occurs because one eye, or both eyes in extreme cases, is out of focus due to myopia / nearsightedness, hyperopia / farsightedness or astigmatism. The unfocused eye (or eyes) "turns off".
- Cataract or cloudy lens: The clouding of the eye's clear lens prevents the image from focusing properly on the retina. This can be a severe form of amblyopia.
What Are the Symptoms of Amblyopia?
Amblyopia can sometimes be difficult to detect, as a young child may not realize that he or she is seeing better with one eye than with the other. However, new methods make it easier to test vision, even in infancy. This is particularly important for any child where there is a family history of misaligned eyes, childhood cataracts or serious eye disease.
One symptom of amblyopia is difficulty with depth perception. If you have ever had to wear an eye patch, you may recall how difficult it was to pour water into a glass. This is an example of poor depth perception. In young children, difficulty in depth perception may not be readily apparent to parents.
Although a National Eye Institute study has proven that amblyopia can be successfully treated in children up to age 17, the best chance for a cure occurs in children before age 2. Therefore, it is recommended that all children have their vision tested by their pediatricians, family doctor or eye doctor as early as possible.
How Is Amblyopia Detected?
Amblyopia is detected by finding a difference in vision between eyes, or poor vision in both eyes. However, it should be noted that having poor vision in one eye does not necessarily mean that you have amblyopia.
In young children, the doctor will observe how well the child is able to follow an object when one eye is covered, as well as his or her reaction to having each eye covered. A baby may cry or attempt to pull off what’s covering the good eye if one eye is amblyopic.
If the vision examination is done by an eye doctor, he or she will also examine the interior of the child’s eye to look for a cataract, inflammation or other problems that may be impacting the child’s vision.
How Is Amblyopia Treated?
In order for vision to improve, the proper signals between the brain and the weak eye must be re-established. For this to happen, the child must use the weak eye. Sometimes this is achieved by wearing eye glasses to correct the underlying myopia, hyperopia or astigmatism. However, if this does not correct vision, patching or covering the stronger eye may be necessary. Depending on the severity, the patching may be required for weeks or months. Even after the vision is restored, part-time patching may be required for an extended period to maintain vision.
Sometimes, your doctor will recommend using a type of eyedrop or contact lens to blur the vision in the stronger eye. Again, this will force the child to use the weaker eye.
If a cataract is determined to be the cause of the amblyopia, surgery may be required to correct the problem. This would normally be done in conjunction with vision correction and patching to restore vision.
While glasses or surgery can correct the cause of the amblyopia, the amblyopia itself must be treated. The weaker eye must be made stronger for normal vision to be restored.
It is important for amblyopia to be treated - and the earlier the better. The good news is that if the problem is detected and treated early, vision improves in most children. However, if the amblyopia is left untreated, there are the following risks:
- The weaker eye may develop a serious and permanent vision defect.
- Depth perception may be compromised.
- Injury or damage to the stronger eye may lead to a lifetime of poor vision.
If your child is diagnosed with amblyopia, you will play the most critical role in his or her vision correction. Children do not like wearing an eye patch, or glasses with one eye patched. As the parent, you must ensure that your child wears the patch to prevent a lifetime of vision problems. While it may not be easy, protecting long term vision will be well worth your efforts.
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