Commonly referred to as "lazy eye", amblyopia is a loss of vision in one or both eyes.
Amblyopia is caused by an abnormality which interferes with the normal use of the eyes and visual development. Commonly, amblyopia is caused by strabismus, a condition in which the eyes are misaligned. With strabismus, often referred to as "cross eyes", the eyes do not work together and one or both eyes turn in, out, up or down.
Amblyopia can also be caused by vision problems such as nearsightedness, farsightedness, and astigmatism. When there is large difference in visual acuity between the eyes, both eyes do not have equal focusing ability. One eye is out of focus because of a stronger degree of nearsightedness, farsightedness, or astigmatism. Therefore, this weaker eye does not develop properly. The eye with the better visual ability does most or all of the visual work, allowing the other eye to become lazy or amblyopic.
More rarely, amblyopia is caused by an eye disease, such as cataracts, which interferes with proper visual development. In addition, amblyopia is inherited in many cases. Whatever the underlying cause amblyopia is the result of long standing suppression of one eye.
In normal vision, both eyes look at an object at the same time and each sends a picture to the brain. These two images are blended into one three-dimensional image. When one eye is weaker than the other, both eyes do not focus on one object at the same time. As a result, two different images are sent to the brain. The image sent by the stronger eye is clear, while the message sent by the weaker eye is blurry.
Since the brain is unable to blend the two images into one picture, a child quickly and unconsciously learns to ignore the image seen by the weaker eye. The normal eye takes over, while the weaker eye becomes lazy from lack of use. If the condition is left uncorrected, the weak eye will eventually develop amblyopia, or a loss of vision.
To correct amblyopia, the weak eye must be forced to work by patching the good eye or using drops to blur vision in the good eye. By impairing vision in the good eye, the weak eye is forced to work until vision in both eyes becomes equal.
Amblyopia must be treated as soon as possible if vision is to be restored. The results of treatment depend on the duration and severity of amblyopia and the age treatment is begun.
Early eye examinations are extremely important in the detection of amblyopia. Prompt treatment is required to restore good vision. If left undetected and untreated beyond early childhood, amblyopia has less chance of being corrected.