How does the laser work?

Many patients ask, “How does the laser correct my vision?” What the laser does is remove tissue from the center of the cornea (in the case of myopia) to flatten the curvature of the cornea to correct nearsightedness; in the case of farsightedness, tissue is removed from the periphery of the cornea to steepen its curvature. The laser essentially reshapes the cornea’s front surface. To do this, the corneal stroma (the tissue beneath the corneal epithelium) must be exposed. This can be accomplished by directly removing the corneal epithelium with a laser (PRK) or by creating a corneal flap with a microderatome (LASIK).

Many types of lasers are used in eye surgery. Argon lasers heat tissue and have been used for years to treat disorders such as diabetic retinopathy and glaucoma. YAG lasers break tissue bonds by creating a shock wave and are used following cataract surgery and to treat certain types of glaucoma. The Excimer laser is a gentle laser uniquely suited to the task of refractive corneal surgery.

The goal is to reshape the cornea so that the rays of light that enter the eye are focused clearly onto the retina. The Excimer laser produces a cool, ultraviolet beam of light (193 nanometers in length) that literally vaporizes tissue away as it breaks carbon-to-carbon bonds without harming adjacent tissue. Tissue is removed in a precise fashion on a microscopic level, leaving adjacent tissue unharmed. This vaporizing process is called photoablation.

The unparalleled precision of the Excimer laser makes it uniquely suited to the task of refractive corneal surgery. Each pulse of the laser removes 0.25 microns of tissues. Think of it as slicing 1/200 of a human hair, 1/28 of a red blood cell, or 1/39 millionth of an inch in 4 billionths of a second. This allows the surgeon to literally sculpt the cornea into a more desirable shape, gently and precisely, and allow the rays of light to focus properly on the retina