Amblyopia


Commonly referred to as "lazy eye", amblyopia is a loss of vision in one or both eyes. Amblyopia is not correctable with prescription lenses, and no detectable damage to the eye or visual system is present. Most commonly the result of poor vision development in children, amblyopia affects approximately 4% of the population.

How does vision develop?

Good vision develops early in life as a result of normal use of the eyes. Although infants can see at birth, vision gradually improves as use of the eyes increases. During the early childhood years, the visual system is in a changeable state and continues to develop with proper use of the eyes. However, if the eyes are not used to capacity, visual ability decreases. After the first 10 years, development of the visual system remains unchanged, whether it is used or not.

What causes amblyopia?

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 a 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. The child favors the eye which sees best and the other eye does not develop fully.

How does amblyopia affect vision?

In normal vision, both eyes look at an object at the same time and each sends a picture to the brain. These two pictures are blended into one three-dimensional image (fusion).

When one eye is weaker than the other, both eyes do not focus on one object simultaneously. 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 (suppression). The normal eye takes over, while the weaker eye becomes lazy from lack of use.

If the condition is left uncorrected, the weak or lazy eye will eventually develop amblyopia, or a loss of vision.

What are the symptoms of amblyopia?

Because it usually causes no symptoms, amblyopia often goes undetected. Unless the child has a misaligned eye or other obvious abnormality, there is nothing to suggest the condition to even the most perceptive parents. The child accepts having one good eye and one poor eye and considers amblyopia to be the normal situation. In most cases, amblyopia must be detected by checking vision.

How is amblyopia treated?

Unfortunately, the treatment of the cause of amblyopia does not cure amblyopia itself. After the causal problem is corrected, amblyopia must be treated separately. 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. Close parental supervision of the child's treatment is necessary to ensure the return of good vision.

Prevention is the best medicine

Early eye examinations are extremely important in the detection of amblyopia. Prompt treatment and strict adherence to the treatment program are required to restore good vision. If left undetected and untreated beyond early childhood, amblyopia cannot be corrected. However, with early detection and treatment, poor vision can usually be improved.

If your child has not had his eyes checked, he should have a complete eye examination.

 

 

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