Dawn Faulkner, age 15, of Butte, Mont., for her question:
WHAT ARE NEARSIGHTEDNESS AND FARSIGHTEDNESS?
Eyes let us carry on almost all of the activities of daily life. They are certainly among our most important sense organs. Defects in the shape of the eye bring about three vision problems. With properly fitted glasses, however, these problems can generally be solved.
Farsightedness comes about when the eyeball is too short. The focus falls behind the retina. Farsighted persons have better vision for distant objects than for near ones and generally wear glasses with convex lenses.
Nearsightedness results when the eyeball is too long and the focus falls in front of the retina. Nearsighted persons have better vision for near objects than for distant ones. They usually wear glasses with concave lenses.
A third defect of the eye is astigmatism. This results from abnormalities in the shape of the cornea or the lens. Some light rays are focused on the retina. But the focus of other rays falls in front or retina. This will very often result in eyestrain and blurring for both distant and nearby objects.
Color blindness bothers some people. This is a condition where a person does not have the ability to distinguish between certain colors. This is an inherited defect of the eye and it cannot be cured.
Strabismus, or cross eyes, is a common defect often found in children. An inability in the action of the muscles that move the eyes causes one eye to turn in or out. To prevent double vision, the image produced by the eye that crosses is ignored by the brain.
Sometimes cross eyes may result in a permanent reduction or loss of vision in the crossed eye. Treatment of strabismus sometimes may require glasses and special exercises. Some doctors recommend the covering of the good eye to strengthen the weak one. Occasionally surgery is necessary.
Newborn babies have very blurred vision. The medical community thinks that perhaps they can see only light and dark for a time. Stereoscopic vision most likely does not develop completely until a child is 6 or 7 years old.
Heredity determines permanent eye color.
As a person grows older, the lens of the eye becomes less elastic and loses some of its ability to change focus. It is often at this time that the problems of nearsightedness and farsightedness occur.
There are also a number of diseases that can effect the eye.
The cornea may at some time be scarred from injury or infection.
The normally transparent lens may become opaque in older persons and bring about a condition called cataracts.