HOW DOES LASIK WORK TO CORRECT NEARSIGHTEDNESS, FARSIGHTEDNESS AND ASTIGMATISM?

In a normal eye (emmetropia), parallel rays of light from the object you are viewing strike the front surface of the eye, the clear dome called the cornea. The cornea bends or refracts these light rays inward so that they meet at a sharp, focused point on the back inner lining of the eye, the retina. As a result, the object is seen clearly and in focus.

In the nearsighted eye, the cornea is too steep and the rays of light are focused in front of the retina. Consequently, the image that falls on the retina is out of focus and the object appears blurred. Astigmatism is a similar condition except that only one part of the cornea is too steep. Therefore only the rays of light that hit the cornea in this steep axis are focused on the retina. Part of the object is in focus, and part is out of focus. Unfortunately, the brain cannot make this distinction so the entire object is viewed as blurred.

Farsightedness occurs when the cornea is too flat and the rays of light focus behind the retina. The result is an out-of-focus image falling on the retina and consequently blurred vision.

The goal of LASIK is to either flatten or steepen the cornea uniformly so that the rays of light are now all normally focused on the retina. In doing so, LASIK can correct nearsightedness, farsightedness and astigmatism.