What is amblyopia?

Amblyopia is an eye condition that develops during childhood in which the vision in one eye is weaker than in the other. It occurs even if the child seems to have no other ocular (eye) problems. Because amblyopia can have serious, permanent effects on your child, it is important that he or she have regular vision tests.

What causes amblyopia?

The most common cause of amblyopia is a major difference in the focusing powers of the two eyes. For example, large differences between the two eyes in astigmatism (irregular shape of the eye) or farsightedness can cause amblyopia. The brain will favor seeing out of the eye that provides a clearer and sharper image and will neglect the other image, which can cause the vision in the weaker eye to get worse.

Another cause of amblyopia is a misalignment (poor positioning) of the eyes (strabismus); for instance, if the eyes are crossed or drift apart. If this happens, the brain tends to favor using the eye that is more frequently aligned (positioned) and ignore the other eye, which leads to a decline in vision.

Other causes of amblyopia arise from anything that is blocking the visual axis (line of vision) of an eye. For example, a cataract (a clouding of the lens), intraocular tumor, or an injury that causes bleeding into the eye or scarring of the front surface (cornea) of the eye may blur the visual axis and lead the brain to favor the stronger eye.

Amblyopia can also develop in both eyes if both images are blurry due to any cause. Cloudy vision in both eyes can interfere with the visual stimulation to the brain, which can lead to a permanent weakening in eyesight.

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