What is a cataract?
A cataract is a clouding of the eye's normally clear
lens. Located directly behind the iris, the lens inhibits
light rays from reaching the retina and results in hazy
or blurred vision. The degree of visual impairment caused
by a cataract varies and depends on how much of the
lens is obstructed by the cataract.
What causes cataracts in infants and children?
Although most cataracts occur in older adults, infants
and children can also be affected. Occasionally, an
infant is born with a cataract. Although infant cataracts
may be inherited or occur as a result of a viral infection
such as German Measles contracted during pregnancy,
it is usually impossible to determine the exact cause.
A cataract may develop during childhood, often as a
result of an eye injury or a disease process involving
other parts of the body. Other causes of childhood cataracts
include abnormal lens growth or the late appearance
of an inherited cataract.
How are cataracts treated?
Some childhood cataracts may only partially cloud the
lens and not interfere with vision. These small cataracts
usually do not require treatment but should be observed
periodically. Moderate size cataracts which do interfere
with vision may require treatment with glasses or treatment
for amblyopia ("lazy" eye). Larger cataracts
which severely interfere with vision require immediate
surgery.
Using microscopic surgical techniques, an ophthalmologist
removes the entire lens or its cloudy contents. All
cataract operations involve incisions into the eye and
on children are usually performed under general anesthesia.
Lasers cannot remove cataracts.
How is vision corrected after surgery?
Once the cloudy lens is removed, the child will need
a substitute lens to focus images on the retina. There
are four ways of restoring focusing power: eyeglasses,
contact lenses, intraocular lenses, and corneal surgery
(epikeratophakia). Regardless of which method of visual
correction is used, the child will need bifocals to
see near objects clearly.
Glasses
Glasses or contact lenses are the most commonly used
means of correcting children's vision after cataract
surgery. Glasses work well for children who have had
cataracts removed from both eyes.
However, a child with a cataract in only one eye presents
a difficult problem. The lens necessary to correct vision
in the operated eye magnifies the size of the image
and creates a situation in which the child sees one
magnified image and one normal sized image. The child's
brain may correct this double image from the operated
eye. This suppression results in an amblyopic or "lazy"
eye. Children who have had cataract surgery in one eye
only need a contact lens, an intraocular lens or epikeratophakia
to restore binocular vision. Cataract glasses can be
used to help maintain useful vision in the operated
eye but they will not restore binocularity.
Contact lenses
Several varieties of contact lenses are available:
rigid, soft daily wear, and extended wear. The type
of contact lens selected depends upon the shape of the
eye, its ability to adapt to a contact, the power of
the lens and the child's or parents' dexterity in handling
the lenses. Several types of contact lenses may be tried
before the proper one is selected. Since an infant's
eye grows rapidly, frequent lens changes may be necessary.
Intraocular lenses
Intraocular lenses are used to correct focus after
cataract surgery in special cases. The plastic intraocular
lens is placed inside the eye during the original cataract
surgery or during a subsequent surgery. The optical
correction is constant, and the images seen by both
eyes are of equal size.
Intraocular lenses are not usually inserted in young
infants because the focusing power changes rapidly in
the young eye and the power of the implanted lens does
not.
Amblyopia: a special problem
Poor vision resulting from amblyopia ("lazy"
eye) can be caused by an infant or childhood cataract.
While the visual system is developing, the brain must
receive clear images from both eyes. If this does not
occur, the visual part of the brain for that eye will
not develop properly.
For this reason, when a cataract develops in infancy
or early childhood, surgery should be performed as soon
as vision is threatened. When older children lose vision
because of a cataract, they usually can be treated in
the same way as adults because their visual development
is complete.
When amblyopia is present, cataract removal is only
the first step in treatment. Proper optical correction
is necessary and the good eye must be patched until
vision improves in the amblyopic eye. Patching the good
eye forces use of the weaker eye. If patching is not
done after cataract surgery, good vision usually fails
to develop. Even after the weak eye has become stronger,
patching may be continued on a part-time basis until
the child is visually mature (about age 9).
Even with prompt therapy, some children develop only
partial visual recovery due to the presence of other
eye defects.
Strabismus
Children with cataracts often develop strabismus (misaligned
eyes). This misalignment is usually treated with eye
muscle surgery to straighten the eyes.
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