For Patients

General Information

Refractive surgery includes several surgical procedures designed to eliminate or reduce the need for glasses or contact lenses. These procedures correct refractive errors by changing the focus of the eye. Common procedures such as LASIK and PRK do this by reshaping the curve of the cornea (the clear front window of the eye) to move the point at which light is focused onto the retina (light-sensitive tissue lining the back of the eye). In cases that refractive surgery cannot be performed Intraocular Refractive Lenses (IRLs-artificial lenses) are placed inside the eye to accurate focus light onto the retina.

Eye Physiology

The shape and other parameters of your eye determines your quality of vision. Light rays enter the eye through the cornea, then through the pupil and the lens. In a normal eye the light rays are focused onto the retina, a light-sensitive tissue lining the back of the eye. Signals from the retina are sent through the optic nerve to the brain, where they are interpreted as the images we see. Refractive errors exist because the curvature of the eye is mismatched to the length of the eye and light rays cannot focus properly on the retina. It is technically very complicated to change the length of the eye (although it has been attempted) so refractive surgery procedures either change the shape of the front surface or add a permanent lens to improve the focus.

The main refractive Errors

Myopia is the most common refractive error, affecting people 20-25%. Myopic patients are nearsighted; they see close objects more clearly, but distant objects are blurry or even indistinguishable. Myopia occurs when the eye is too long or the cornea is too steep. As a result, light rays entering the eye fall in front of the retina instead of directly on it. The condition can be inherited and usually starts in childhood and stabilizes in the late teens or early adulthood. Traditionally, corrective lenses such as eyeglasses or contact lenses have been prescribed to refocus light entering the eye directly onto the retina.

Hyperopic patients are farsighted; they can focus on more distant objects, but close-up objects appear blurry. Hyperopia occurs when the eye is shorter than normal or the cornea is too flat. As a result, light rays are not focused by the time they reach the retina. In young people, the eye lens can sometimes correct the focus in hyperopic eyes. With aging, the eye lens loses this ability and the vision blurs. This is why many hyperopic patients do not become aware of their condition until they enter their 20s.

Astigmatism occurs when the curve of the cornea, and sometimes the lens, is uneven-steeper in one direction. Almost everyone has some degree of astigmatism, but for some the uneven curve causes light rays to focus on many points in the eye and distorts both close and far vision.

With the help of glasses or contact lenses, the light beams change direction and focus on the retina. Refractive surgery changes the curvature of surface of the eye or the optical attributes of lens of the eye and improves the sight. The result of intervention is seeing clearly without glasses or contact lenses. It is essential for the refraction to be stable and the eye to be in a healthy condition.