Refractive Surgery...

"Refraction" refers to the way the eye focuses light, the source of everything we see. There are three basic elements that determine the eye's ability to focus light:

The shape of the cornea, the eye's transparent outer membrane

The power of the lens, which lies behind the pupil and completes the focusing process

The length of the eyeball

Normal vision

In an eye with normal vision light rays are refracted in such a way that they meet at a light-sensitive membrane called the retina, which is located at the back of the eye. There, light images are changed into electrical impulses and sent by the optic nerve to the brain's vision-processing center.

Refractive errors occur when light rays entering the eye do not focus properly on the retina. Refractive errors are not diseases, but rather normal differences in visual ability. There are three basic types of refractive errors: myopia (nearsightedness), hyperopia (farsightedness), and astigmatism.


In myopia, the most common type of refractive error, the cornea is too curved, the lens is too powerful, or the eyeball itself is too long. As a result, light rays are refracted too sharply and meet at a point in front of the retina. For this reason, faraway objects appear blurry.





People with hyperopia, on the other hand, experience just the opposite problem. Because the cornea is too flat, the lens is too weak, or the eyeball is too short, light rays do not have enough space to come together before reaching the retina. As a result, hyperopic people see distant objects more clearly than nearby objects.






Astigmatism, which often occurs with either myopia or hyperopia, is an irregular curvature of the cornea. It causes light rays to reach the retina in different locations and thus prevents the eye from focusing clearly at any distance.





A fourth type of refractive error, presbyopia, occurs as the eye ages and the lens loses its ability to change focusing for close objects. Hence the need for bifocals or reading glasses.