The images you see are the result of your cornea and retina working together. Your cornea, acting as the eye's window, receives the light that enters your eye and focuses it on the retina (the back of the eye). This bending and focusing of light is known as refraction. Often the shape of the cornea and the eye are not perfect and can prevent you from seeing clearly. These imperfections in the focusing power of the eye are called refractive errors.

There are three primary types of refractive errors: myopia, hyperopia and astigmatism. Myopia, also known as nearsightedness, causes difficulty with seeing distant objects clearly. Persons with hyperopia, or farsightedness, see distant objects clearly while up-close images appear blurred. Astigmatism is a distortion of the image on the retina caused by irregularities in the cornea. Another condition, presbyopia, often appears around the ages of 40-50 and causes the need for reading glasses.

Refractive surgery is a description given for the different types of surgeries that are performed to correct refractive errors – myopia, hyperopia and presbyopia. Refractive errors are present in over 50% of the adult population and are generally correctable with eyeglasses or contact lenses. However, many patients would prefer to avoid the expense and inconvenience of glasses and contacts, and refractive surgery may allow them to do this.