When should vision be tested?
It is recommended
that all children have their vision checked by their
pediatrician, family physician or ophthalmologist (medical
eye doctor) at or before their fourth birthday.
Most physicians test
vision as part of a child's medical examination. They
may refer a child to an ophthalmologist (a medical
eye doctor) if there is any sign of an eye condition.
New techniques make
it possible to test vision in infants and young children.
If there is a family history of misaligned eyes, childhood
cataracts or a serious eye disease, an ophthalmologist
can check vision even earlier than age three.
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:
- 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.
- 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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