Refractive surgery is a surgical procedure used to correct eye's refractive defects. In recent years, tremendous advancements have been made in this field. After refractive surgery, many patients report seeing better than they had at any other time in their lives.
The excimer laser is a form of ultraviolet chemical laser which is commonly used in eye surgery and semiconductor manufacturing typically uses a combination of an inert gas (Argon, krypton, or xenon) and a reactive gas (fluorine or chlorine). Under the appropriate conditions of electrical stimulation, a pseudo-molecule called a dimer is created, which can only exist in an energised state and can give rise to laser light in the ultraviolet range. This light is exceptionally well focussed and capable of very delicate control, and is well absorbed by biological matter and organic compounds. These properties make excimer lasers well suited to precision micromachining organic material (including certain polymers and plastics), or delicate surgeries such as eye surgery.
Rather than burning or cutting material, the excimer laser adds enough energy to disrupt the molecular bonds of the surface tissue, which effectively disintegrates into the air in a tightly controlled manner through ablation rather than burning. Every laser pulse can remove an infinitesimally amount of corneal tissue, i.e., 0.25 micron per pulse. Thus excimer lasers have the useful property that they can remove exceptionally fine layers of surface material with almost no heating or change to the remainder of the material which is left intact.
The first excimer laser was invented in 1971 by Nikolai Basov, V. A. Danilychev and Yu. M. Popov, at the P. N. Lebedev Physical Institute in Moscow, using a xenon dimer (Xe2) excited by an electron beam to give stimulated emission at 172 nm wavelength. A later improvement was the use of noble gas halides (originally XeBr), invented (and patented) in 1975 by George Hart and Stuart Searles of the United States Government’s Naval Research Laboratory.
In 1980 - 1983, Dr. Samuel Blum was working with Dr. Rangaswamy Srinivasan and James Wynne at IBM’s T. J. Watson Research Center when they observed the effect of the ultraviolet excimer laser on biological materials. Intrigued, they investigated further, finding that the laser made clean, precise cuts that would be ideal for delicate surgeries. For their work, they were awarded patent #4,784,135 and Dr. Blum and Dr. Rangaswamy Srinivasan were elected to the National Inventors Hall of Fame in 2002.
All vision correction surgeries work by reshaping the cornea so that light traveling through it is properly focused onto the retina located in the back of the eye. There are a number of different surgical procedures used to reshape the cornea, including:
LASIK: Short for LAser in-Situ Keratomileusis. This procedure is used to correct vision in people who are nearsighted, farsighted, and/or have astigmatism. During LASIK, vision is corrected by reshaping underlying corneal tissue so that it can properly focus light into the eye and onto the retina. This procedure differs from others in that a flap is made in the outer layer of the cornea so that the underlying tissue can be accessed.
PRK: Short for PhotoRefractive Keratectomy. This procedure is used to correct mild to moderate nearsightedness, farsightedness, and/or astigmatism. During PRK, an eye surgeon uses a laser to reshape the cornea. This laser, which delivers a cool pulsing beam of ultraviolet light, is used on the surface of the cornea not underneath the cornea, like in LASIK. Therefore, no cutting is required.
LASEK: Short for LASer Epithelial Keratomileusis. This is a newer form of laser vision correction that combines many of the benefits of LASIK and PRK. However, unlike LASIK and PRK, there is no cutting or scraping of the eye, instead an epitheal flap is created using a 20% alcohol solution. It is used to treat nearsightedness, farsightedness, and astigmatism.
EPI-LASIK: the technique is similar to PRK or LASEK; the difference is in the epithelial removal technique. It is used a blunted microkeratome to achieve a smooth, repeteable and accurate superficial lamella of epithelium and anterior elastic membrane.
Are these procedures safe and effective?
The results of corrective surgeries are very promising: at least 98% of people treated for myopia (between -1 D to -9), astigmatism (between 1 to 3 D) or hyperopia (between +1 to +3 D) are satisfied with their surgery. On the other hand, before surgery, it is important that you undergo to a preoperative full eye examination. Refractive surgeries require healthy eyes that are free from retinal problems, corneal scars, and any eye disease.
Excimer laser surgery has minimal side effects and most of all are temporary. Infection resulting from laser surgery are extremely rare, they can occur in one-tenth of one percent of patients. If an infection does result from surgery, it generally means added discomfort and a longer healing process. With ultimate laser platforms, undercorrection or overcorrection are very limited: more than 99% ofeyes treated are within 1 diopter of the intended refractive target.
Corneal haze is a faint opacity of the corneal tissue: it occurs as a part of the natural healing process after surface ablation procedures. It usually has no effect on the final outcome of vision after surgery and can only be seen through an eye examination. Rarely, this haze may affect a patient’s vision.
Sometimes the effects of surgery gradually disappear over a period of several months. When this happens a second surgery is often recommended to achieve permanent results.
Halo effect and glare are in general transient simptoms during the first months following high myopic correction: these optical effects can occur in dim light. As the pupil enlarges, the untreated area on the outside of the cornea produces a second image.
As technology progresses more and more, it is very important that you explore all options and possibilities before deciding which vision repair treatment is right for you.