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What Is Amblyopia?
Amblyopia is poor
vision in an eye that did not develop normal sight during
early childhood. It is sometimes called "lazy eye." When one
eye develops good vision while the other does not, the eye
with poorer vision is called amblyopic. Usually, only one eye
is affected by amblyopia. The condition is common, affecting
approximately 2 or 3 out of every 100 people. The best time to
correct amblyopia is during infancy or early childhood.
Parents must be aware of this potential problem if they want
to protect their child's vision. |
How Does Normal Vision Develop?
Newborn infants are
able to see, but as they use their eyes during the first
months of life, vision improves. During early childhood years,
the visual system changes quickly and vision continues to
develop. If a child cannot use his or her eyes normally,
vision does not develop properly and may even decrease. After
the first nine years of life, the visual system is usually
fully developed and usually cannot be changed. The development
of equal vision in both eyes is necessary for normal vision.
Many occupations are not open to people who have good vision
in one eye only. |
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If the vision in one eye should be lost later in life from an accident or illness, it is
essential that the other eye have normal vision. Without normal vision in at least one eye,
a person is visually impaired. For all of these reasons, amblyopia must be detected and
treated as early as possible. |
What Causes Amblyopia?
Amblyopia is caused by
any condition that affects normal use of the eyes and visual
development. In many cases, the conditions associated with
amblyopia may be inherited. Children in a family with a
history of amblyopia or misaligned eyes should be checked by
an ophthalmologist early in life. Amblyopia has three major
causes:
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- Strabismus (misaligned eyes): Amblyopia occurs most commonly with misaligned or crossed
eyes.
The crossed eye "turns off" to avoid
double vision and the child uses only the better eye.
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- Unequal focus (refractive error): Refractive errors are eye conditions that are
corrected by wearing glasses. Amblyopia occurs when one eye
is out of focus because it is more nearsighted, farsighted
or astigmatic than the other. The unfocused (blurred) eye
"turns off" and becomes amblyopic. The eyes can look normal
but one eye has poor vision. This is the most difficult type
of amblyopia to detect and requires careful measurement of
vision.
- Cloudiness in the normally clear eye tissues: An eye disease such
as a cataract (a clouding of the eye's natural lens) may
lead to amblyopia. Any factor that prevents a clear image
from being focused inside the eye can lead to the
development of amblyopia in a child. This is often the most
severe form of amblyopia.
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How Is Amblyopia Diagnosed?
It is not easy to
recognize amblyopia. A child may not be aware of having one B
eye and one weak eye. Unless the child has a misaligned eye or
other obvious abnormality, there is often no way for parents
to tell that something is wrong. Amblyopia is detected by
finding a difference in vision between the two eyes. Since it
is difficult to measure vision in young children, your
ophthalmologist often estimates visual acuity by watching how
well a baby follows objects with one eye when the other eye is
covered. If one eye is amblyopic and the good eye is covered,
the baby may attempt to look around the patch, try to pull it
off or cry. |
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Poor vision in one eye does not always mean that a child has amblyopia. Vision can often be improved by prescribing glasses for a child. Your ophthalmologist will also carefully examine the interior of the eye to see if other eye diseases may be causing decreased vision. These diseases include:
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- Cataracts
- Inflammations
- Tumors
- Other disorders of the inner eye
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How Is Amblyopia Treated?
To correct amblyopia,
a child must be made to use the weak eye. This is usually done
by patching or covering the B eye, often for weeks or months.
Even after vision has been restored in the weak eye, part-time
patching may be required over a period of years tomaintain the
improvement. Glasses may be prescribed to correct errors in
focusing. If glasses alone do not improve vision, then
patching is necessary. Occasionally, amblyopia is treated by
blurring the vision in the good eye with special eye drops or
lenses to force the child to use the amblyopic eye.
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Amblyopia is usually treated before surgery to correct misaligned eyes, and patching is
often continued after surgery as well. If your ophthalmologist finds a cataract or other
abnormality, surgery is required to correct the problem. After surgery, glasses or contact
lenses can be used to restore focusing, while patching improves vision. Amblyopia cannot
be cured by treating the cause alone. The weaker eye must be made Ber in order to see
normally. Prescribing glasses or performing surgery can correct the cause of amblyopia,
but your ophthalmologist must also treat the amblyopia. If amblyopia is not treated,
several problems may occur:
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- The amblyopic eye may develop a serious and permanent visual defect
- Depth perception (seeing in three dimensions) may be lost
- If the good eye becomes diseased or injured, a lifetime of poor vision may
be the result.
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Your ophthalmologist can give you
instructions on how to treat amblyopia, but it is up to you
and your child to carry out this treatment. Children do not
like to have their eyes patched, especially if they have been
depending on that eye to see clearly. But as a parent, you
must convince your child to do what is best for him or her.
Successful treatment mostly depends on your interest and
involvement, as well as your ability to gain your child's
cooperation. In most cases, parents play an important
role in determining whether their child's amblyopia is to be
corrected.
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Loss of Vision Is
Preventable
Success in the
treatment of amblyopia also depends upon how severe the
amblyopia is and how old the child is when treatment is begun.
If the problem is detected and treated early, vision can
improve for most children. Sometimes part-time treatment may
have to continue until the child is about nine years of age.
After this time, amblyopia usually does not return. If
amblyopia is first discovered after early childhood, treatment
may not be successful. Vision loss from strabismus or unequal
refractive errors may be treated successfully at a much older
age than the amblyopia caused by cloudiness in tissues in the
eye. |
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