Wednesday, December 15, 2010

Refractive Eye Surgery

Refractive eye surgery is any eye surgery used to improve the refractive state of the eye and decrease or eliminate dependency on glasses or contact lenses. This can include various methods of surgical remodeling of the cornea or cataract surgery. The most common methods today use excimer lasers to reshape curvature of the cornea. Successful refractive eye surgery can reduce or cure common vision disorders such as myopia, hyperopia and astigmatism.

The first experimental studies about refractive surgery were published in 1896 by Lendeer Jans Lans, an ophthalmology teacher in Holland, where he developed a theoretical work proposing penetrating corneal cuts to correct astigmatism. In 1930 the Japanese ophthalmologist Tsutomu Sato made the first practical attempt to perform such surgery in military pilots. He practiced radial cuts in the cornea to correct effects by up to 6 diopters, but this procedure was soon rejected by the medical community because of the high rate of corneal degeneration. In 1963, in the Barraquer ophthalmologic clinic (Bogotá, Colombia) Ignacio Barraquer developed the first proficient refractive surgery technique called keratomileusis, meaning corneal reshaping.

There are two surgical techniques to perform a refractive eye surgery:
1) Automated lamellar keratoplasty (ALK): The surgeon uses an instrument called a microkeratome to cut a thin flap of the corneal tissue. The flap is lifted like a hinged door, targeted tissue is removed from the corneal stroma, again with the microkeratome, and then the flap is replaced.
2) Laser Assisted In-Situ Keratomileusis (LASIK): The surgeon uses a femtosecond laser to cut a flap of the corneal tissue (usually with a thickness of 100-180 micrometres). The flap is lifted like a hinged door, but in contrast to ALK, the targeted tissue is removed from the corneal stroma with an excimer laser. The flap is subsequently replaced. Another method of creating this flap is by using a procedure called IntraLase, in which a femtosecond laser is used to create the flap. Proponents of this method assert its superiority over "traditional" LASIK, but there have been no conclusive independent studies to prove that this is a true statement.