A cataract is the clouding of the eye’s normally clear lens. Located directly behind the iris (the colored part of the eye), the lens focuses the light on the retina (the light sensitive tissue on the back of the eye). A cloudy lens inhibits light rays from reaching the retina and results in hazy or blurry 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 adults as part of the aging process, 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 (Rubella) contracted during pregnancy, it is usually impossible to determine the exact cause. A cataract may develop during childhood, often as a result of eye injury or a disease process involving other parts of the body. Other causes of childhood cataracts include abnormal lens growth or late appearance of an inherited cataract.
How are cataracts treated?
Some childhood cataracts may only partially cloud the lens may 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 with 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 cataracts operations involve incisions into the eye and on children are usually performed under general anesthesia. Laser 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 cornel surgery (epikeratophakia). Regardless of which method of visual correction is used, the child will need bifocals to see near objects clearly.
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 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 by suppressing (turning off) the 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.
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 parent’s 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 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 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. The long-term safety of intraocular implants in children has not been established.
Focusing power can be corrected with an epikeratophakia corneal graft, a specially ground piece of cornea surgically stitched onto the surface of the eye. As with any surgical procedure, complications can occur.
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.
Even with prompt therapy, some children develop only partial visual recovery due to the presence of other eye defects.
Children with cataracts often develop strabismus (misaligned eyes). This misalignment is usually treated with eye muscle surgery to straighten the eyes.
American Academy of Ophthalmology
The Eye M.D Association