Vision Correction Surgery

LASIK Eye Surgery

The most common vision correction procedure today is LASIK.  LASIK eye surgery is a surgical procedure intended to reduce a person’s dependency on glasses or contact lenses.

• read more about LASIK

Refractive Errors

The cornea is a part of the eye that helps focus light to create an image on the retina. It works in much the same way that the lens of a camera focuses light to create an image on film. The bending and focusing of light is also known as refraction. Usually the shape of the cornea and the eye are not perfect and the image on the retina is out-of-focus (blurred) or distorted. 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.

Refractive Error Types

• Myopia, or nearsightedness, causes difficulty seeing distant objects as clearly as near objects.
• Hyperopia, or farsightedness,  causes difficulty seeing near objects as clearly as distant objects.
• Astigmatism is a distortion of the image on the retina caused by irregularities in the cornea or lens of the eye.
• Surgical procedures aimed at improving the focusing power of the eye are called refractive surgery.
• In LASIK surgery, precise and controlled removal of corneal tissue by a special laser reshapes the cornea changing its focusing power.

How the eye works

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.

Additional Refractive Surgeries

Radial Keratotomy or RK and Photorefractive Keratectomy or PRK are other refractive surgeries used to reshape the cornea. In RK, a very sharp knife is used to cut slits in the cornea changing its shape. PRK was the first surgical procedure developed to reshape the cornea, by sculpting, using a laser. Later, LASIK was developed. The same type of laser is used for LASIK and PRK. Often the exact same laser is used for the two types of surgery. The major difference between the two surgeries is the way that the stroma, the middle layer of the cornea, is exposed before it is vaporized with the laser. In PRK, the top layer of the cornea, called the epithelium, is scraped away to expose the stromal layer underneath. In LASIK, a flap is cut in the stromal layer and the flap is folded back.

Another type of refractive surgery is thermokeratoplasty in which heat is used to reshape the cornea. The source of the heat can be a laser, but it is a different kind of laser than is used for LASIK and PRK. Other refractive devices include corneal ring segments that are inserted into the stroma and special contact lenses that temporarily reshape the cornea (orthokeratology).