Kornmehl Laser Eye Associates

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Kornmehl Laser Eye Associates

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An Overview of Laser Vision Correction – Part 2

Photorefractive Keratectomy (PRK)

The procedure that originally made wide use of the excimer laser was photorefractive keratectomy (PRK), first performed in 1987. Instead of using a microkeratome to remove the corneal disc, PRK uses the laser to accurately sculpt the cornea one microscopic layer at a time. PRK has seen vast improvements since those early days.

PRK sculpts the cornea by first removing the epithelium, the outer protective layer of the cornea. The laser works its way down into the stroma, or structural part of the cornea, where the real reshaping takes place. The epithelium then grows back over the next 48 to 72 hours. PRK presents some inconveniences. First, PRK can leave your eyes sore for 24 to 48 hours after surgery while the eye heals. Second, because the corneal surface is left exposed, patients experience blurred vision for almost a week following surgery.


In 1990, researchers conceived of ways to avoid these side effects associated with PRK; they developed a new procedure called LASIK, a type of refractive surgery in which a laser is used to reshape the cornea, improving vision. LASIK is an acronym for laser-assisted in situ keratomileusis.  The component words of LASIK are defined as:

LASer-assisted – performed with the excimer laser

In situ – performed on the cornea after a flap of corneal tissue has been lifted

Keratomileusis – a process of carving the cornea to reshape it

During a LASIK procedure, an extremely thin flap is created in the outermost layers of the cornea using a thin blade called a microkeratome or a laser. This flap is gently lifted back like a hinged lid, exposing the corneal tissue beneath. The cornea is then precisely sculpted by the excimer laser into a new shape to correct the patient’s vision. The flap is set back in place and is held in position by the eye’s natural suction.

Clinical trials on LASIK began in the United States in 1991. A broad series of clinical investigations culminated in its approval by the FDA in 1999.

How LASIK Corrects the Eye’s Focus

How can a laser beam correct vision? The excimer laser is uniquely suited to the task of refractive corneal surgery because it ablates, or vaporizes, tissue by breaking apart the molecules without creating damaging heat. The unparalleled precision of the excimer laser makes it the ultimate reshaping tool. The laser is so precise that it would take 600 pulses to break through one strand of human hair. This precision allows Dr. Kornmehl to sculpt the exposed corneal bed, gently and precisely, into a more desirable shape that allows rays of light to focus properly on the retina. The result is improved vision.

Learn more Boston LASIK Surgery, make your consultation with Dr. Kornmehl today!