Issue Date: April 30, 2006
Focus on eyes
Here's why even small changes affect your quality of sight.
Within the same week, my 15-year-old daughter was fitted for glasses, and my father underwent surgery for cataracts. Although their specific problems are quite different, the interventions both had will distinctly improve the quality of their lives. Those of us with normal eyesight may have a hard time relating, but we all know the eyes are wonderful and complex organs. In fact, a significant portion of our brain function is required just to interpret the information our eyes provide.
Even small changes in our eyes can affect how we see. Although there are many causes of vision problems, the most common one is a change in refraction, or the way light enters the eye. As light enters the eye through a round, smooth cornea, it is bent, or refracted, and sent through the clear lens and toward the back of the eye (the retina). The bent light rays focus directly on the retina, which processes and sends information to the brain, where it is interpreted as sight. If not properly bent, the light rays focus either in front of or behind the retina. As a result, the retina's ability to process information is compromised, and the brain interprets a blurred image.
Optometrists and ophthalmologists use glasses to correct these refractive problems. When properly prescribed, eyeglasses make up for the error in refraction from the cornea to give us clear vision. Fortunately, recent surgical advances have made altering the structure of the eye (such as the cornea and the lens) possible to correct refraction problems, reducing or even eliminating the need for glasses.
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3 major types of refraction problems
Nearsightedness. "Myopia" occurs when the focal point of the refractive images falls in front of the retina instead of directly on it. Those with myopia can see objects that are near clearly; distant objects are blurred.
Farsightedness. "Hyperopia" occurs when the focal point of the images falls behind the retina. People with hyperopia see distant objects clearly, but near objects are blurred.
Astigmatism. This condition occurs if the cornea's shape is irregular, causing light rays to scatter through the lens toward the retina. Consequently, light focuses on several focal points in the eye instead of one. Astigmatism often occurs along with either farsightednessor nearsightedness. People with astigmatism have difficulty seeing fine detail close-up or at a distance. Correction requires glasses that bend light rays at various angles over the misshapen cornea.
Contributing editor Tedd Mitchell, M.D., is medical director of the Wellness Program at the renowned Cooper Clinic in Dallas.
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