The cornea of the eye is an important structure. In addition to providing cover for the inner structure of the eye, it also provides refection to the light entering the eye. This refection is an important part of the overall image formation process. If the shape of the cornea is damaged, the image either forms in front of or beyond the retina of the eye. In all such cases, the retina will not receive adequate information for proper formation of the image. The result is blurred image that is often the case in far- or near sightedness.
Refractive surgery is actually an umbrella term for several surgeries that aim to correct the shape of the cornea.
For people suffering from nearsightedness, refractive surgery aims to reduce the curvature of the cornea. The result is a decrease in the focus of the eye so that the images now form in front of the retina.
For people suffering from farsightedness, refractive surgery aims to increase the curvature of the cornea. The result is an increase in the focus of the eye so that the images now form at the right spot.
The most well known example of refractive surgery is LASIK. This procedure is used to eliminate or reduce dependency on corrective glasses and contact lenses. In this procedure, the cornea of the eye is reshaped using a laser.
Refractive surgeries are usually performed under very strict criteria because of the inherent risks involved in the procedures.