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Medical Author:

J. Bradley Randleman, MD

J. Bradley Randleman, MD

Dr. Randleman received his BA degree from Columbia University in New York City. He earned his MD degree from Texas Tech University in Lubbock, Texas, where he was elected to the Alpha Omega Alpha Medical Honor Society. He completed his residency training at Emory University, serving as Chief Resident in his final year. He then completed a fellowship in Cornea/External disease and refractive surgery at Emory University.

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Coauthor:

John F. Payne, MD

Medical Editor:

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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What is LASIK?

LASIK stands for laser in situ keratomileusis, which means using a laser underneath a corneal flap (in situ) to reshape the cornea (keratomileusis). This procedure utilizes a highly specialized laser (excimer laser) designed to treat refractive errors, improve vision, and reduce or eliminate the need for glasses or contact lenses. This laser procedure alters the shape of the cornea, which is the transparent front covering of the eye. Though the excimer laser had been used for many years before, the development of LASIK is generally credited to Ioannis Pallikaris from Greece around 1991.

How does LASIK work?

During the LASIK procedure, a specially trained eye surgeon first creates a precise, thin hinged corneal flap using a microkeratome. The surgeon then pulls back the flap to expose the underlying corneal tissue, and then the excimer laser ablates (reshapes) the cornea in a unique pre-specified pattern for each patient. The flap is then gently repositioned onto the underlying cornea without sutures.

What is refractive error?

In the human eye, the front surface (cornea) and lens inside the eye form the eye's "focusing system" and are primarily responsible for focusing incoming light rays onto the surface of the retina, much like the lenses of a camera focus light onto the film. In a perfect optical system, the power of the cornea and lens are perfectly matched with the length of the eye and images are in focus; any mismatch in this system is called a refractive error, and the result is a blurred image at some location.

What are the primary types of refractive error?

Myopia (nearsightedness): In people with myopia, the mismatch in focusing power and eye length causes distant objects to be blurry and near objects to be clearer.

Hyperopia (farsightedness): In people with hyperopia, the mismatch in focusing power and eye length causes near objects to be blurry and distant objects to be relatively clearer.

Astigmatism: In people with astigmatism, either the corneal or lens shape is distorted, causing multiple images on the retina. This causes objects at all distances to appear blurry. Many people have a combination of either myopia or hyperopia with astigmatism.

How do glasses or contacts improve vision in people with refractive errors?

Glasses or contact lenses are used to compensate for the eye's refractive error by bending light rays in a way that complements the eye's specific refractive error. In contrast, LASIK and other forms of refractive surgery are intended to correct the eye's refractive error to reduce the need for other visual aids.