Understanding The Treatment For Farsightedness

If you are farsighted, or hyperopic, light comes to an imaginary focal point behind your retina. The farsighted eyeball is too short from front to back for the power of the cornea, causing a blurred image up close. (The length of your eye may be too short from front to back, or your cornea may be flatter than normal, or both.) Almost all newborn babies are farsighted; those who aren't often become markedly nearsighted as adults. Since many hyperopic patients can see distant objects well when they are young, they are called farsighted.

To correct farsightedness, a laser surgeon makes the center of the eye's window steeper by removing tissue in a carefully blended circular pattern around the mid-periphery of the cornea. Even though the laser is not aimed at the line-of-sight, the effect of treatment is directly over the pupil. After surgery, the central cornea has a steeper curve with more light blending ability that can focus incoming light nearer the retina instead of behind it. Although both hyperopic and myopic LASIK procedures remove tissue to the same depth for the same number of diopters of refractive error, much more tissue is removed from the cornea to treat farsightedness. Refractive surgery for farsightedness can improve both near and distance vision, although you may still need glasses to read if you are over forty.

While it is true that the farsighted eye focuses light at a theoretical point beyond the retina, hyperopia is more complex than this brief explanation implies. Without the added light bending power of the flexible crystalline lens inside your eye, even parallel light rays reflected off distant objects "focus" behind your sensitive photoreceptors. Causing an even more blurred image, the divergent rays from close objects "come together" still further behind your retina than light from far away.

So to help you understand farsightedness on a practical level, you need to keep in mind how the two lenses of your eye - your powerful fixed corneal lens and your adjustable crystalline lens inside your eye - work together to focus light. In the youthful eye, the flexible crystalline lens can "morph" itself, becoming thicker to bring close objects into view and remaining flatter to look in the distance. Instantly changing shape, this amazing lens becomes rounder (more highly curved) for near vision to add more focusing power to your optical system. Doctors call this process "accommodation".

The crystalline lens of the farsighted eye not only must become thicker for near vision, but also for distance. In some hyperopic patients, this elastic lens is unable to compensate enough to allow clear close vision. If you need correction for farsightedness, both of your lenses working in concert lack enough focusing power to "pull" the image forward onto your retina. Put yet another way, the combined power of your corneal and crystalline lenses fails to bend light enough to focus it on your photoreceptors.

If you are farsighted, you may suffer from fatigue or headaches because of the way your eyes focus. Normally, when you look at a close object, both eyes naturally move inward toward each other. The same nerves that control the muscles that cause your eyes to converge also govern the focusing power of your crystalline lens. Your adjustable lens and your eye muscles are designed to work together to provide good single, binocular near vision. But when a farsighted person looks in the distance - as each lens adjusts to overcome hyperopia - the eyes try to turn toward the nose. Since you must look straight ahead to see far away, your brain instantly counteracts this automatic response and tells the eye muscles to move your eyes outward. Such focusing problems can cause eye strain, double vision, or both.