A child is not born being able to see. Vision develops as an image is formed in the eye and is transmitted to the brain. If the brain is denied an image, pathways are not formed which will allow the brain to process the picture. This is called amblyopia. If the brain is denied vision in both eyes from birth, the eyes may develop a jumpy, searching movement. This is called nystagmus. There is a critical period in a child's life in which these pathways can be formed. This time is most critical during the child's first year of life. After the first year it becomes increasingly difficult to improve vision. Limited improvement can be made after 8 years of age.

When a child is diagnosed with cataracts, they must be removed immediately if they are hindering vision development. However, without a lens inside the eye, the light will no longer focus and form an image on the retina. Spectacles or a contact lens must be fit quickly, so the visual pathway to the brain can start to form. Spectacles, however, can cause image distortion, prismatic effects, anisometropia, and aniseikonia, resulting in a less than perfect image. All these effects are eliminated by using contact lenses. A contact lens acts as if it were part of the eye; wherever a child looks, he will be looking through the lens center. Spectacles are not possible in the case of unilateral aphakia because of the image size difference (aniseikonia) induced.

Unlike an adult aphake, a child's eye is continuing to grow. As the eye length increases, the power needed to correct the child's vision will decrease. This causes frequent changes in a childís contact lens. It is necessary to follow a child with frequent examinations to monitor a child's visual development.

Because of the importance of stimulating vision, having the lens off the eye for any length of time may result in vision loss. Therefore, we require the parents to keep a back up pair of contact lenses at home, in case of loss or breakage.

An infant is seen every one to two weeks during the initial thre months of fitting. Then the baby is seen every month for the rest of the first year of life. Infants typically require a change in contact lens fit at 6-8 weeks old, 6-9 months old and around 1 year old. After one year, a child is seen less frequently, every two to three months, and requires fewer changes. The average child goes through eight lenses per eye during the first year of life and four lenses per eye thereafter, including fit changes, loss, and breakage.

These lenses are prosthetic devices, replacing the lens of the eye. They correct vision beyond that which is obtainable with spectacles. It is necessary to monitor the fit and make changes as the eye grows to insure health and optimum development of the visual pathway. The use of contact lenses in pediatric aphakia is a true medical necessity.

Glossary

Amblyopia
Decreased vision in one or both eyes without detectable anatomic damage in the eye or visual pathways. Usually uncorrectable by eyeglasses.
Aniseikonia
Unequal retinal image sizes in the two eyes, usually from different refractive errors.
Anisometropia
Unequal refractive errors in the two eyes; usually at least one diopter different.
Aphake
Patient whose crystalline lens has been removed, e.g., after cataract extraction.
Cataract
Opacity or cloudiness of the crystalline lens, which may prevent a clear image from forming on the retina. Surgical removal of lens may be necessary if visual loss becomes significant. May be congenital or caused by trauma, disease, or age.
Nystagmus
Involuntary, rhythmic side-to-side or up and down eye movements.

Christine Sindt, OD

Last Reviewed: 2005

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