Definition:
Amblyopia is a condition in which a person’s vision does not develop properly in early childhood because the eye and the brain are not working together correctly. Amblyopia, which usually affects only one eye, is also known as “lazy eye”.
Cause:
Amblyopia is caused by the lack of normal stimulation to the visual centers of the brain. Vision is a learned and developed skill that requires precise focusing of light on the retina along with subsequent stimulation to the visual center of the brain. Interruptions to this experience during the first 7 years of life can severely hinder the development of clear sight. Amblyopia can also occur when the eyes do not work together as a team. When one eye crosses inward or turns outward, the brain tends to use one eye and ignore the other. Consequently, the visual cells of the brain that normally receive information from the misaligned eye do not develop maximally, resulting in blurred sight. Some major causes of amblyopia are as follows:
- Strabismus - A misalignment of the eyes is the most common cause of functional amblyopia. The two eyes are looking in two different directions at the same time. The eyes may turn in, out, up, or down. Strabismus may be diagnosed at birth, or it may develop later in childhood. The brain is sent two different images and this creates confusion. Images from the misaligned or “crossed” eye are turned off to avoid double vision.
- Anisometropia - A difference of refractive states exists between the two eyes (in other words, a difference in prescription between the two eyes). For example, one eye may be more nearsighted (unable to see clearly objects that are far away) than the other eye, or one eye may be farsighted (able to see distant objects better than nearby ones) and the other eye nearsighted. Because the brain cannot fuse the two images, the brain suppresses the blurrier image, causing the eye to become amblyopic.
- Cataract - Clouding of the lens of the eye causes the image to be blurrier than the other eye. The brain prefers the clearer image, and the eye with the cataract may become amblyopic.
- Ptosis - If light cannot enter the eye because of the drooping (a lowered, sagging, or slumped position) lid, the eye is essentially going unused, which can lead to amblyopia. However, ptosis is rarely related to the development of amblyopia, unless the droopy eyelid completely obscures the pupil.
Characteristics:
Many people with amblyopia, especially those who are only mildly so, are not even aware they have the condition until tested at older ages, since the vision in their stronger eye is normal. However, people who have severe amblyopia may experience associated visual disorders, most notably poor depth perception.
A person with amblyopia experiences blurred vision in the affected eye. However, children often do not complain of blurred vision in the amblyopic eye because this seems normal to them.
Early treatment is advisable, because if left untreated, this condition may lead to permanent vision problems. Treatment options include vision therapy exercises or prescription eyeglasses. People with amblyopia may need to wear an eye patch over their stronger eye in order to force the affected eye to function as it should
Resources:
www.afb.org
www.DrBillFoundation.org
www.familyconnect.org/eyeconditions.asp
www.en.wikipedia.org/wiki/amblyopia
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