The Insight on Eyesight
In order to decide whether laser vision correction is a viable option for you, it is important to first understand how the eye works and why people need glasses or contact lenses to see well.

The eye works much like a camera; its primary function is to focus light. For the eye to see, light rays must be bent or "refracted" to meet at a single point through the cornea, the clear window at the front of the eye that provides most of the focusing power. Light then travels through the lens, where it is fine-tuned to focus properly on the retina, the nerve layer that lines the back of the eye and connects to the brain. The retina acts like the film in a camera, and clear vision is achieved only if light from an object is precisely focused onto it.

If the light focuses either in front of or behind the retina, the image you see is blurred. A refractive error means that the shape of eye structures does not properly bend the light for focusing.

Having 20/20 vision means seeing at 20 feet what a normal person sees at 20 feet. However, if vision is measured at 20/40, it means a person has to walk up to 20 feet to see the same size letter that someone with 20/20 vision could see at 40 feet.
And so on.

People whose best-corrected visual acuity (what they see using glasses or contact lenses) is less than 20/200 in the better eye are considered legally blind, even though they still have enough vision to get around. Prior to laser surgery, Jeri Goldstein's visual acuity without her contact lenses was measured at 20/400 in her right eye and 20/200 in the left eye. Following surgery, her eyesight without contacts stands at 20/25 and 20/20, respectively.