What Is Refractive Eye Surgery?
By Gray Rollins
Refractive eye surgery is a type of eye surgery that is used to rectify refractive errors of the eye and decrease dependency on corrective lenses such as eyeglasses and contact lenses. Successful refractive procedures can reduce myopia or nearsightedness, hyperopia or farsightedness, and astigmatism or elongated corneas. A number of different procedures exist for refractive eye surgery depending upon the type and severity of the refractive error.
There are four main types of refractive eye surgery procedures: flap and photoablation procedures; corneal incision procedures; thermal procedures; and implants. Currently, the most common refractive eye surgeries involve the use of lasers to reshape the cornea.
Flap procedures involve cutting a small flap in the cornea so that the tissue underneath can be reshaped to correct the refractive error. LASIK, short for Laser Assisted In-Situ Keratomileusis, is the most popular refractive surgery and is used to correct myopia, hyperopia, and astigmatism. The LASIK procedure involves using a microkeratome or IntraLase to cut a flap into the stroma, moving the flap out of the way, removing excess corneal tissue with an excimer laser, then replacing and smoothing out the flap. LASEK is best suited for individuals with thin or flat corneas. The LASEK procedure uses a small trephine blade to cut into the shallow epithelium, after which the eye is bathed in a mild alcohol solution to soften the edges of the epithelium. The flap is gently moved out of the way so that an excimer laser can remove excess corneal tissue, after which the flap is replaced and smoothed out. Epi-LASIK, like LASEK, involves a shallow cut into the epithelium, but makes use of epikeratome to create a thin epithelium sheet for removal instead of the harsher blade and alcohol.
Photoablation, the second stage in flap procedures, makes use of ultraviolet radiation to remove excess corneal tissue. PRK, or photorefractive keratectomy, was the original laser eye surgery procedure. PRK involves numbing the eye with local anesthetic eye drops, and reshaping the cornea by destroying miniscule amounts of tissue from the surface of the eye. The laser used, an excimer laser, is a computer-controlled ultraviolet beam of light. It burns cool so as not to heat up and damage the surrounding eye tissue.
Corneal incision procedures such as radial keratotomy and arcuate keratotomy use miniscule incisions in the cornea to alter its surface and correct refractive errors. Radial keratotomy, or RK, uses a diamond tipped knife to make a number of spoke-shaped incisions in the cornea. The result of the incisions is that the cornea flattens out, minimizing the effects of myopia. Arcuate keratotomy, or AK, is very similar to RK. The diamond knife is used to cut incisions that are parallel to the edge of the cornea, as opposed to the spoke-shaped incisions of the RK procedure. These procedures have been much less common with the emergence of laser-assisted refractive eye surgeries.
Thermal procedures use heat to correct temporarily hyperopic refractive errors, or farsightedness. The thermal keratoplasty procedure involves putting a ring of 8 or 16 small burns on the eye immediately surrounding the pupil. The application of the heat increases the slope of the cornea, making it steeper, through thermal contractions. There are two main types of thermal keratoplasty. Laser Thermal Keratoplasty, or LTK, is a no-touch procedure that uses a holmium laser. Conductive Keratoplasty, or CK, uses a high-frequency electric probe.
The final type of refractive eye surgery involves the use of implants. Implantable contact lenses, or ICL, can be used to correct severe levels of myopia, hyperopia, and astigmatism. The implants are actually tiny contact lenses that are inserted through a small incision in the side of the cornea. Implants are seated so they sit immediately in front of the eye's natural lens just behind the cornea. ICL works in conjunction with the eye's natural lens to refocus light on the retina and produce a crystal clear image.
Each of these procedures has its advantages and disadvantages, and not all individuals are suitable candidates for refractive eye surgery. Individuals who are interested in learning more about surgical options should contact their ophthalmologist for more information about these procedures, as well as inquire about other new cutting-edge procedures. Since ophthalmologic surgery is constantly growing and changing with emergence of new technologies and methods, there are always new techniques in development. As new equipment is developed and methods refined that can improve the success and minimize the side effects of refractive eye surgery, new procedures will emerge to replace outdated techniques.
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