Seeing well without contact lenses and glasses is the dream of millions of Americans and modern medical science has enabled that dream to come true (Caster, 8). Since first grade, Dede Head, a 30-year-old fitness trainer in North Carolina, has worn glasses to correct sever nearsightedness and astigmatism. Over the years she became accustomed to wearing glasses and contacts, but this has limited many important aspects of her life, including sports. She then heard of a laser eye surgery that ?supposedly?, helped to correct a person’s vision by means of lasers.
She immediately signed up for the procedure and ever since that day, she has not worn glasses or contacts. Dede is just one of the eight hundred-fifty-thousand people who have undergone a procedure by the name of LASIK or Laser In-Situ Keratomileusis. If surgical procedures were movies, LASIK would be this years box office smash as it has received much media coverage and many praises; however, not that many people know what LASIK is, what the advantages and disadvantages are, and most importantly if LASIK is right for them (Buratto, 1). LASIK is basically a type of laser surgery which can help correct nearsightedness (myopia), which is the inability to see distant objects, farsightnedness (hyperopia), which is the inability to see close, and astigmatism, the inability to focus light waves evenly. LASIK has grown greatly in the last year, mostly because of 4 reasons; it is fast (procedure takes about 5-10 minutes), safe, painless, and the results are almost always prolific.
The eye is just like a camera because it works by focusing light waves that pass through it. Light rays that enter the eye must first pass through the most outer layer of the eye called the cornea. The cornea performs 2/3 of the focusing process, the remainder of is then completed by the crystalline lens which further focuses the light on the retina. This requires extreme precision in that the focused light must fall exactly at the level of the retina (Gallo, 126). The retina is a nerve tissue that carpets the inner surface of the eye, much like wallpaper covers all aspects of a wall. The retina converts the light into electrical signals, which are transmitted to the brain by the optic nerve.
Just as a camera cannot produce clear photographs of the image if the incoming light is not focused on the film, we cannot produce a clear vision if the cornea and crystalline lens do not focus the light precisely on the retina. This is where LASIK steps in. A laser is a device that creates a very special kind of light energy that is usually invisible to the human eye (Caster, 16). In LASIK, ophthalmologists use a certain type of laser called the excimer.
By using invisible ultraviolet light, the excimer is able to break covalent bonds between molecules. What sets excimer aside from other lasers used in medicine is the wavelength used. At one-hundred ninety-three nm (nanometers), excimer lasers remove tissue by breaking the covalent without creating much thermal energy (Slade, 25). This allows for precise removal of tissue with minimal surrounding tissue damage. The very thin layer of the cornea that is removed, changes the curvature of the cornea ever so slightly, thus then results in a change in the light focusing ability.
In nearsightedness (myopia), light rays from distant objects are not focused on the retina, but instead they are focused in front of the retina (See Figure 1). Therefore to correct nearsightedness in a LASIK procedure, the curvature of the cornea must be decreased or in another words made flatter by removing corneal tissue in a disc-shaped pattern, or from the central cornea. A computer determines the exact pattern and number of pulses that are needed to do this. In farsightedness (hyperopia), light rays from distant objects are focused not onto the retina, but behind it (See Figure 1).
To correct this, the central portion of the cornea must be made steeper; and this is accomplished by removing corneal tissue in a donut shaped pattern, or in another words more from the peripheral areas. Eyes with astigmatisms focus light waves unevenly because of the irregular shape of the cornea; football shaped as opposed to the usual round, basketball shaped corneas. The excimer laser can remove corneal tissue asymmetrically, and so the end result is a round, symmetrical surface (Sloat, 90). LASIK, did not just develop suddenly overnight in some ophthalmologist’s mind; however, LASIK is part of an evolved procedure (Gallo, 127). Today’s vision correction revolution dates back decades through the sheer genius, persistence, and ingenuity of Professor Jose Barraquer (Slade, 8). Refractive surgery, which is the type of surgery LASIK is characterized as, started in Bogota, Columbia in 1948 when Barraquer started performing a procedure called Freeze Keratomileusis.
This procedure involved adding a disc of corneal tissue (donated from another person) with a predetermined curvature in the cornea giving it structure. In a journal found 2 decades after this procedure, it stated that patients who had myopia could see better after the procedure; however he stated a few months after the surgery, that some patients would lose their eyesight due to infection. The reason for this was that Barraquer used an unsterilized shaver to cut the cornea. It was not until the late 1970’s that refractive surgery resurfaced when US surgeons visited the Soviet Union. The surgeons brought back a procedure called Radial Keratotomy (RK) which made spokelike incisions in the cornea by using a handheld diamond scalpel.
The results were good, but scientists noticed that the incisions structurally weakened the eye. Scientists and doctors worked for 2 decades to develop Radial Keratotomy into a procedure that was both safe and produced good results. Then in 1994, a company by the name of Summit Technologies developed the first excimer laser that could be used for surgery. A year after, the Food and Drug Administration (FDA) approved this excimer laser and stated that it could only be used to correct mild nearsightedness in a procedure called Photorefractive Keratectomy (PK).
In PRK, surgeons scrape away the very outer layer of the cornea (less than 5% thickness of the entire cornea) and then use the excimer laser to vaporize the underlying corneal tissue to a predetermined depth (no more than fifty percent thickness of the cornea). These results were very good as 90 percent of the cases showed that the patients achieved at least 20/40 vision, which is the usual standard to pass a driver’s license test; however, the surgery had many drawbacks. While the procedure itself was not painful, patients had significant pain and discomfort for almost a week after the surgery (Gallo, 129). Worst of all, it often took a week to even see anything and six months to get the full benefits of the surgery (Gallo, 129).
Dr. Stephen Slade, a refractive surgeon, summarized the procedure well by saying, ?PRK works well, but it hurts and the results take too long. To be honest, patients don’t like it. ‘soon after PRK was introduced, surgeons began testing a procedure called Laser In-Situ Keratomileusis, which was first partially introduced by the father of ophthalmology, Barraquer in 1950 (Slade, 8). Keratomileusis is derived from the Greek root keras (horn-like cornea) and mileusis (carving) and basically it is a procedure that involves slicing and peeling back the outer layer of the cornea (anterior cornea), leaving a hinge on one side, while the laser sculpts the tissue underneath (corneal stroma).
After the excimer laser is done, the flap is placed back to where it was before, and no stitches are needed because the corneal flap heals by itself when left to dry. You are probably wondering if they still used the diamond scalpel, and the answer thankfully is not. Surgeons use a very precise instrument called the microkeratome (See Figure 3) which makes LASIK very unique compared to other surgeries. This device is a mechanical shaver that has a sharp blade, which moves back and forth at very high speeds (See figure 2).
After a suction ring has been placed on the cornea, the microkeratome is place on top of the cornea and advances across it at very small increments creating a flap that is only 1/3 inch in diameter. This instrument cuts the cornea at a uniform thickness and creates a portion of the cornea uncut. After the suction ring and the microkeratome have been removed, the corneal flap is folded back (See Figure 4), exposing the middle portion of the cornea. Also in LASIK surgery, the excimer laser can be used at different frequencies and therefore produce different desired results in the same patient. Each laser pulse in a LASIK procedure removes ten-millionths of an inch of corneal tissue in twelve-billionths of a second while in a PRK procedure, the laser removes about twice as much in about the same time. The amount of corneal tissue removed depends on how nearsighted or farsighted the patient is (Gorman, 60).
The more nearsighted a patient is the more tissue must be removed to obtain a flatter cornea, and the same goes with farsightedness, except the cornea has to be made steeper. Back when Barraquer started Keratomileusis In Situ, he noticed that he was having great success with patients who had myopia and did not know why patients who had hyperopia and astigmatism were not enjoying the same results. Surgeons even today notice, that after LASIK, patients who have myopia before the surgery get better results than patients who have other vision ailments (such as hyperopia, astigmatism, and presbyopia) (Gallo, 128). Ophthalmologists now believe that the reason has to do with how the excimer laser reshapes the cornea (Gallo, 128). In a patient who has myopia, the laser makes the cornea flatter while in a hyperopic situation, the laser makes the cornea steeper. The problem does not come during the surgery but after it when the cornea bed reshapes itself to match the ?new? cut cornea.
They call it the cornea bed because it is just like a bed because as you lie on a mattress, it will reshape itself to the contour of your body. Once the cornea is made flatter, the cornea bed has no problem reshaping itself to the new contour; however, this is not always the case for hyperopia and astigmatism. The corneal bed, which is located behind the outer layer of the cornea, has trouble reshaping itself to either a steeper or narrower shape. Ophthalmologist do no fully understand why this occurs, but they do urge that LASIK provides better results for people who suffer from myopia and therefore, that is why the vast majority of people who undergo LASIK do so to correct nearsightedness (Buratto, 9). The results of LASIK are astounding (Gallo, 129). The obvious goal of LASIK is to get a vision of 20/20, which is perfect vision.
20/20, 20/40, and so on are measures of visual acuity; a person with 20/40 needs to stand twenty feet away from something that a person with 20/20 can see fine from forty feet away. Last March, the Journal of Ophthalmology stated that 3 months after the surgery, seventy-percent of the patients who have had LASIK, have 20/20 vision. A follow up 2 years after the surgery showed that sixty-three-percent kept the ?perfect vision? while ninety-nine-percent had at least 20/40 vision. The amount of vision improvement generally is tied to the degree of nearsightedness and farsightedness before the surgery. Dr. Stephen Slade, who is one of the pioneers of LASIK said, ?The less nearsighted or farsighted you are, the more likely you’ll get 20/20.
For low myopes, ninety-five percent can get 20/20. For high myopes, the figure might drop to sixty percent. ?Usually, for every good thing that comes along, there are some unfavorable circumstances that follow; however, there are not too many complications or side effects in LASIK (Shovlin, 113). Complications are very rare, but they will be more common in patients with high nearsightedness, farsightedness, and astigmatism because they require more laser treatment.
Also no patient has ever become blind after a LASIK procedure; however, there are a list of possible complications that can result in decreased vision after the surgery. One complication results from the anterior cornea (flap) being placed unevenly after the laser treatment, which usually results in a corneal haze. Another possible complication is that of an infection, which only occurs in . 5 percent of the time.
However, by far, the most common complication is under or over correction, which are due to the laser removing either too much tissue or too little tissue respectively. Under correction results from lack of corneal tissue being removed and is usually fixed with a procedure called ?touch up? (another mini LASIK procedure but without any further cuts). If too much corneal tissue is removed, the problem is a lot more serious because surgeons must perform a Keratophakia, in which they have to add corneal tissue. Under correction and over correction are the main reasons that all patients do not receive 20/20 vision, and that is why no patient can ever be guaranteed perfect vision.
Last January, a review in LASIK of 1,062 eyes found that complications occur in about 5 percent of the cases. Tests before the procedure are now being taken more seriously than before, because those tests determine how much laser treatment is needed. While the recovery period of LASIK is remarkably short, forty-percent of people who had the procedure see halos or starbursts around bright lights for several months (Buratto, 5). Ophthalmologists believe this effect seems to be caused by the edge created between the treated and the untreated part of the cornea which bends and distorts the light as it enters the eye.
Seeing halos or starbursts usually occurs during night, when the pupil dilates and the edge of the cornea falls right into view and for this reason, people with exceptionally large pupils should not undergo LASIK. These starburst effects, as ophthalmologists call it, usually go away after a few months. Little research is available on LASIK’s long-term safety and effectiveness, but there is information available on PRK. Last year, a review in ophthalmology traced eighty-three British patients who underwent PRK in 1990, and found no serious complications in any of them. This is attributed to the amount of untouched, deep cornea (approximately fifty percent of the entire cornea), which maintains the eyes original overall shape. This is opposite of RK which left only 10% of the untouched cornea (Voelker, 1494).
Despite its increasing popularity, LASIK is not for everyone. People with extra-thin corneas are not good candidates of this surgery because the surgeon does not have enough tissue to work with. Ophthalmologists also turn away people who have rheumatoid arthritis and diabetes because they have problems with dry eyes, and are hence poor healers. As people approach forty years old, they begin to lose the ability to change their focus from far to near (presbyopia), but don’t worry, it is natural in everyone. Baby boomers who have LASIK to try to correct presbyopia, usually trade their distance glasses in for reading glasses (or vice versa).
Surgeons are now answering this problem with ?mono-vision?, which is correcting one eye for far distance and the other for focusing on close distances. After this procedure, the brain adapts, using each eye for different functions; however, patients often experience blurry midrange vision and have depth perception problems. ?Most patients don’t mind it, but it drives some people nuts,’says Dr. Slade. ?There is a revolution happening in vision correction,’says Dr. Guy Kezirian, a refractive surgeon in Arizona, and spokesman for the International Society of Refractive Surgery.
?We’re seeing a stampede of people interested in a surgical alternative. ? The question I ask is, why not? Glasses can be very inconvenient, and contacts can be a hassle, so why not venture in this vast, growing field of LASIK? LASIK is not just an eye operation anymore, it is a 2 billion dollar a year industry that has revolutionized the way surgery is looked at. Usually costing two thousand dollars per eye, LASIK is not a surgery that anyone can afford, especially since it is not covered by insurance. Yet when asked, a LASIK patient consistently states that the surgery was one, if not the, best thing which they have ever done for themselves: no worries of sleeping with contact lenses and contracting a sight threatening infection (Slade, 254). No fear of scuba diving or swimming with contacts, and no fear of waking up 3 a.
m. after having heard noises downstairs, and not being able to find your glasses. LASIK surgery gave Diane, a forty-five-year-old doctor assistant, a newfound sense of freedom. Before the surgery, she couldn’t clearly see her feet when she was in the shower, but now after LASIK, she is taking rock-climbing lessons with her twelve-year-old daughter; something she would have never done if she were wearing glasses or contacts.
Stories like this are becoming common as Americans flock to eye doctors at record rates for this ?surgical fix?. LASIK is blossoming like a flower in the Fertile Crescent and soon everybody will be taking advantage of its wondrous gift that it provides; the gift of sight.
