How the eye works

Your eyes work on much the same principle as a camera. The iris, or colored part of the eye, acts as the shutter to regulate the amount of light that enters the eye. If there is too much light, the iris will cause the pupil (small hole in the center of the iris) to shrink; if there is too little light, the iris will enlarge the pupil to allow more light to enter. The cornea (the clear "window" at the front of the eye) and the lens, located behind the pupil, serve to focus light rays onto the retina in the back of the eye. The retina then transmits the "picture" to the brain, which is what actually "sees" the image.

Unfortunately, not everyone is blessed with perfect eyes. For millions of Americans with vision problems, daily life can be difficult at times. If you have ever lost or broken your glasses or have lost a contact lens, you know how hard it can be just to get through the day without them. Even simple things we often take for granted can suddenly become difficult and can sometimes lead to embarrassing or even dangerous situations. Recognizing a co-worker or friend across a room, keeping an eye on your children at a playground, driving your car to work -- everyday situations that depend on your clear eyesight.

All of our eyes work the same, yet they can be different in many ways. The wide variety of color and shapes of eyes gives people variety and personality. But while some differences can be beautiful, others can lead to vision problems.

Myopia (Nearsightdness)

If the curvature of the cornea is too steep or the shape of the eye is elongated, light rays entering the eye come to a focal point before reaching the retina. Because the light is not focused directly on the retina, the resulting image is blurry and details are hard to make out, similar to taking a picture with a camera out of focus. To a nearsighted (myopic) person without glasses, objects viewed up close are more clear, but objects in the distance appear blurry. Myopia is an inherited condition usually starting in childhood and stabilizing in the late teens or early twenties.

Hyperopia (Farsightedness)

If the curvature of the cornea is too flat or the eye is shorter than normal, light rays entering the eye are focused behind the retina instead of directly on it. The resulting image the retina sends to the brain is out of focus. However, most people do not notice vision problems with hyperopia until they start to get older -- around forty years of age. Although hyperopia is an inherited condition, children and younger people with hyperopia can usually see well up close and far away without glasses because the lens inside the eye can compensate for the misshapen cornea or eye. But with age, the muscles inside the eye can no longer make up for this focus problem. By their late thirties or early forties, most hyperopes have a hard time seeing things clearly both up close and far away and will have to use glasses or some other type of optical correction.

Astigmatism
When the curvature of the cornea is uneven (the cornea is more oblong instead of perfectly spherical), the eye cannot focus the light rays directly onto one point on the retina as a normal eye can; instead, the eye may focus the light rays on multiple points in front of and behind the retina. Because astigmatism makes it difficult for the eye to focus, the end result is blurred vision.

Presbyopia (Mid-Life Reading Crisis)
All people will eventually develop presbyopia. It's a natural process that your eyes go through as you age. Normally, as you reach your early to mid 40's you will start to have difficulty reading or looking at objects close-up with your glasses on. As your eye ages, the lens inside the eye has difficulty focusing, making it hard to read or see objects up close.

Chances are, you will probably have to wear reading glasses to read or do any kind of close-up work. If you're nearsighted (myopic), you will most likely be able to see small objects up close and read by simply taking your glasses off, or if you prefer, by wearing a pair of bifocal glasses to correct for both near and distance vision. If you are farsighted (hyperopic), you will have great difficulty seeing objects both close-up and far away without your glasses and will need to either wear bifocals or carry both distance and reading glasses.

Please realize that presbyopia will affect everyone, regardless of whether you have had Laser Vision Correction or not. If you are past your mid 40's, while you may be able to see clearly in the distance after Laser Vision Correction, you will probably have to wear reading glasses to read or see objects close-up.

At this moment in time, there are no approved surgical treatments for presbyopia available. However, scientists and physicians are working on several different techniques that may turn out to be effective alternatives to reading glasses. Most likely it will be at least several years before any treatment for presbyopia is available in the United States.