Talking about mathematics in terms of truth, beauty, and sculpture might seem to require quite a mental stretch. But let's take that thought by English philosopher and mathematician Bertrand Russell and stretch those four concepts even further by applying mathematics, truth, beauty, and sculpture to cornea surgery—the cutting, carving, sculpting, and, at times, replacing of our corneas, our windows on the world.
Let's consider the various corneal surgical techniques and procedures in terms of these four concepts.
Mathematics. Every portion or segment of the eye can theoretically be precisely measured, and the measurements can be compared to that of the mythical "perfect" eye.
Beauty. Like any smooth-running and well-designed machine, the eye is a thing of beauty in its own right.
Sculpture. Every eye has its own shape and form. To change the eye itself, you have to change its shape, sculpting a new shape for its surface out of the living material already there.
Truth. There are long and complex philosophical arguments that could be made about the nature and role of surgery. There is also a very short one: Is this operation—and the risk it involves—really necessary?
The cornea is the transparent lens that covers the front of the eye. It is one of the body's few living tissues that contains no blood vessels, a fact that bestows two major advantages.
First, it makes the cornea easy to see through. Second, because certain cells in the bloodstream cause the body to reject transplanted organs and tissues, not having any circulation in the cornea increases the odds of a corneal transplant being successful. Please keep all of this in mind as we continue. We'll start out with corneal transplants.
Corneal Transplants—New Eyes for Old
The single most common transplant surgery performed in the world today, corneal transplants have been around for more than 100 years.
Why are corneal transplants so common? Think of the cornea as the crystal covering a watch. It protects the delicate timekeeping mechanism and also allows us to view the face of the watch. But you know how easily your watch crystal can get banged up and scratched. In a similar way, even though the cornea is protected by the eyelids and the blink reflex, it still gets traumatized.
Because of congenital abnormalities, disease, or injury, the cornea may become cloudy or scarred in a way that interferes with normal vision. One of the most common medical reasons for a corneal transplant is eye infection stemming from the herpes simplex virus. For reasons no one really understands, some people are more prone to recurring herpes infections than others. While usually not a major problem, sometimes the infection can lodge deep in the cornea and set up an immune reaction that results in severe inflammation. It can last for months, causing scarring that can make a corneal transplant necessary.
Cornea Swapping's Shaky Start
By the time the first successful human corneal transplant was performed in 1888, people had been talking about the subject—and even doing some experiments—for hundreds of years.
Although serious medical research didn't start until the 1750s, the medical history books mention a charlatan and quack named Chevalier Taylor who roamed Europe in the Middle Ages, making a living by peddling "secret remedies" and potions to the great unwashed, uninformed, and unlettered, which, back then, pretty well summed up more than 99 percent of the population.
Charlatan and quack though he was, Taylor did know what the cornea was, and that if it were scarred or fogged, it could cause blindness. He suggested two ways to solve the problem: Either shave or sand the cornea smooth. He even left precise instructions about how to do it. For shaving, he suggested, "Pare off the excrescence with a small curved knife, leaving as few inequalities as possible." And for sanding: "Scrub the eye with a small brush made of barley bristle."
While history does record his advice, it does not reveal if it was ever followed.
By the mid-1700s, the European medical community was looking at the cornea with a slightly more scientific approach, talking and writing about the possibility of removing cloudy corneas and replacing them with glass, other material, or corneas taken from animals.
Actual transplants—between animals—began in the early 1800s. Then in 1844, a Dr. Kissam in New York transplanted a pig cornea into a human. Later that same year another doctor tried a similar operation using a sheep's cornea. Neither of these "heterografts" (different species transplants) worked.
Those failures did not do much to popularize the experimental operation, especially because all surgery up until that point was done without the benefit of anesthetics.
But in 1846 ether was introduced in Boston, and by 1850 chloroform had been used as an anesthetic in an eye operation. This helped set the scene for an 1859 operation in which glass was implanted in a human cornea.
Finally, almost 30 years later, Dr. Arthur von Hippel, in Germany, was ready to try his hand, ideas, and skill at actually transplanting a human cornea. He had figured out that transplants between members of the same species had a better chance of working. He had also developed a new type of device to remove the old cornea and then cut the replacement cornea so it would fit exactly in its place. In 1888 he performed the first successful human-to-human transplant.
Corneal infections are also becoming more common among contact lens wearers. Most contact lens–related infections are caused by bacteria. A parasitic organism called Acanthamoeba has been getting a lot of publicity recently. It causes a serious and hard-to-treat eye infection in a small percentage of contact lens wearers. It is most likely to show up in people who use extended-wear contact lenses or who make their own contact lens saline solution from distilled water they buy in a store. Such distilled water is not sterile and is not meant for use in the eye.
The Acanthamoeba has also been found in hot tubs and even in ground soil, so it is very common in our environment. It is believed to cause infections only when a large dose enters the eye and the eye's surface is then irritated by a contact lens or minor injury.
Taking into account everyday trauma, infection, and the fact that many common eye surgery procedures can injure the delicate inner lining of the cornea, it's a wonder doctors don't have to do more corneal transplants.
The number of corneal transplants increases every year. In 1984 there were more than 24,000 performed in the United States. In 1987 there were more than 35,000. And this year? It all depends on the number of available corneas.
A corneal transplant simply replaces the opaque or scarred cornea with a clear one that has been donated in the same way that hearts, kidneys, and other organs are donated after death.
The surgery itself is very delicate, and much of it is performed while the surgeon is looking at the cornea through a special operating microscope.
First the opaque cornea is removed with a trephine, a round knife that operates a bit like a cookie cutter. The donor cornea is cut to match the hole left by the trephine. Using extremely fine sutures that are thinner than a human hair, the surgeon then sews the new cornea into place.
The operation usually lasts about an hour and is sometimes performed on an outpatient basis. As a rule, the patient is urged to resume a normal lifestyle as soon as possible after the operation. The sutures are usually removed after several months.
The Gift That Truly Keeps On Giving
You can help the blind see. All you have to do is let your corneas be used after you die.
Donated corneas are used for regular transplants, and for research and training. No donated cornea is wasted. As medical knowledge grows and surgical expertise increases, more and more people will be able to see, but only if there are enough corneas available.
Every year people spend months on waiting lists, waiting for a new cornea. And as the number of transplants performed grows, so too does the number of people on the waiting lists. You can help change that by electing to become a cornea donor. In many states there is an organ donor card already attached to each driver's license. In other areas, it's possible to get an organ donor card from a local hospital or eye or organ bank. In any event, talk over your decision with your family. Let them know that you want to help with the gift of sight.
To be useful for either a transplant or research, a cornea must be removed very shortly after death. So to save time and prevent additional emotional strain or trauma, it can help to have a "family policy" about the matter. Every cornea is useful, whether it's a child's or a senior citizen's, and the donor doesn't have to have 20/20 vision.
More than 80 percent of all corneal transplants are successful the first time they are tried. When they do not work the first time, the procedure can be tried again and again. Some patients have received five or six transplants before one "works."
If the transplant is rejected, it will normally happen within the first year following the surgery, and the patient is usually the first one to realize that there are problems. The first indication of rejection can include a slight change in vision, unusual redness, or sensitivity to light. That's what a patient notices. What an ophthalmologist notices is a line of inflammatory cells marching across the inner surface of the cornea like an invading army, leaving destroyed cells in their wake. This can lead to corneal swelling and total transplant rejection.
Getting Along with Your New Cornea
If you are facing comeal transplant surgery, you may hear general statements about what the "average" person will feel like afterward or be able to do, or how long until "normal" vision returns. Just remember that there is no "average" human being. Each and every one of us reacts to things in slightly different ways.
Do not be surprised or necessarily alarmed if your own recovery is different from the so-called, and in many ways mythical, normal one. If you are in doubt or concerned about anything, call your doctor.
When you go home, it is hoped that you will be able to resume living a normal, active life. Here are some considerations to keep in mind. Your doctor will tell you if there are any special circumstances that would change these in your case.
Expect That ...
Call Your Doctor If There Is ...
If spotted early, rejection can often be halted with the use of steroid eyedrops.
Researchers are working on ways to reduce the odds of rejection by developing better ways to match donor and recipient tissues. While this can result in a longer wait for a suitable donor cornea to become available, it lessens the chance of a subsequent rejection.
Radial Keratotomy—The Controversial Cuts
According to modern folk legend, "way back" in 1973 a young nearsighted Russian boy got into a fight with another lad who obviously didn't buy into the concept that there is something intrinsically unfair about hitting a kid wearing glasses. The nearsighted lad wound up with a piece of broken glass stabbing into his eye.
It was a tragedy. At least it started out that way, and it might have stayed a tragedy—a blinding tragedy—except for the fact that the boy's doctor was the noted Russian surgeon, Dr. S. N. Fyodorov.
When Dr. Fyodorov operated on the boy, he removed the broken glass. Then he sewed closed the cuts the glass shards had made in the boy's cornea. But now something was different. The minor changes made in the cornea by the cutting and sewing were enough to alter the shape of the boy's cornea.
Three days later, when the bandages were removed, the boy could see clearly—without his glasses.
Radial keratotomy, often referred to as RK, is the eye operation that Dr. Fyodorov pioneered to correct nearsightedness and allow nearsighted people to throw away their glasses and contact lenses.
There is no doubt that he developed the procedure, although a similar procedure was tried and abandoned 40 years earlier by a Dr. Sato, a Japanese ophthalmologist who cut the cornea on its inner surface.
There is, however, some doubt about when Dr. Fyodorov developed his procedure. Did he get the idea after seeing the results of his operation on the boy with the cut cornea? Or had he already worked out the procedure in theory before the injured boy presented him with the opportunity to use it? Was there really a nearsighted boy who had his glasses broken in a fight?
The main controversy, however, is not over how or when Dr. Fyodorov developed RK, but over the procedure itself.
"Am I Still Me?"
When they unwrapped the bandages, my once-blind mother looked out at the world and saw it—through a dead man's eyes. And she cried.
She cried for the man whose eyes she had, for his family, for her own dead eyes, for her years of blindness. She cried with the joy of being able to see again. She also cried with fear. There was a stranger, or at least a part of a stranger, living inside of her.
"Am I still me?"
She'd ask that question from time to time as we sat up half the night discussing the world in general and our lives in particular, and speculating on the nature of the anonymous man who had bequeathed her his vision.
"Am I still me?"
It's a question that more and more of us have to come to grips with every day. There are people walking, working, and running around the world today with mechanical pacemakers marking the beat of their lives by keeping their hearts beating. Millions also pause from time to time to think about the synthetic tubing replacing their arteries, the donated blood flowing through those tubes and arteries, the metal pins in their thighs, the artificial hip joints, their false teeth, their new corneas, even their contact lenses and their wigs.
Where does it stop? Where does the real you stop and the artificial you begin?
Did the "persona" of Terry Fox, the Canadian athlete and cancer victim who ran across Canada, include the artificial leg he ran on?
"Am I still me?"
To answer that, first answer the following.
"Who am I? What am I? When I say 'me,' just what am I referring to?"
While you're at it, also ask yourself what you are willing to endure to go on being you. When people are considered for transplants, their mental fitness is measured, too. In many cases merely wanting to live is not enough. There must be a driving, consuming passion to survive. That passion must be able to look at a piece of plastic, or steel, or another person's eyes or heart and say: "Mine! Me! That's part of me! That's me! Myself!"
But what, exactly, is self?
A Canadian transplant surgeon, Dr. Calvin Stiller, of London, Ontario, once answered that question this way: "Fundamentally, we are not physical beings, but spiritual. Our physical shell is constantly adapting and being adapted to the environment to protect that spiritual self."
"Am I still me?"
When they unwrapped the bandages, my once-blind mother looked out at the world and saw it—through a dead man's eyes. And she cried.
"Am I still me?"
Flattening the Cornea
Compared with most eye surgery, the RK procedure is relatively simple. Four to 16 "radial" cuts are made in the cornea. They look like the spokes on a bicycle wheel. This cutting changes the shape of the eye and, when done right, can correct the eye's focusing power.
Nearsighted—or myopic—people usually have elongated eyes, so the images their corneas "project" to the retina come into sharp focus before they reach the "screen." By the time they do reach the retina, the images have gone out of focus again.
The RK surgery flattens such corneas so the images they project arrive at the retina in perfect focus. It's like readjusting the lens on a slide projector.
Myopia, or nearsightedness, is the single most common focusing or refractive problem in the world. Most of the people you see wearing glasses are myopic. When you consider how many of these millions of nearsighted people hate having to wear either glasses or contact lenses, it's easy to understand how the RK operation could become popular with patients and lucrative for doctors.
American doctors quickly picked up the RK technique and have performed tens of thousands of the operations. All in all, the results have been surprisingly good. The professional doomsayers who predicted indiscriminate surgery and disastrous complications have, for the most part, been proven wrong.
Most people who undergo the procedure are quite happy with the results, and many recommend the operation to their friends. But even though many patients seem pleased with RK, the medical profession is divided over the ethics of the procedure. Most ophthalmologists are loath to slice into a healthy eye. Nearsightedness, after all, is not a disease. The myopic eye is not sick.
Some doctors opposed to the procedure point out that, historically, eye surgery has been generally reserved for pathological conditions such as cataracts and glaucoma. Doctors taking the other view point out that, historically again, there wasn't much that could be done to the eye through surgery except for those pathological conditions. Today, there is; there is RK, cosmetic surgery for the eyes. After all, they add, cosmetic surgery is big business.
Cosmetic surgeons say they help heal a patient's self-esteem by correcting a physical condition that has caused the patient emotional pain. Their attitude is that whether that emotionally disturbing condition be a weak chin, a large nose, or nearsighted eyes, if it can be fixed and the patient desires it, they are willing to fix it.
When Things Go Wrong
The problem is that not all RK procedures turn out the way they were supposed to. Some patients are overcorrected, leaving them farsighted instead nearsighted. Some are not corrected enough, leaving them still nearsighted, sometimes as much as before the surgery. In either case, the patient has had the joy of paying for an operation that did not work, and then having to go out and buy brand-new glasses.
Even when the results are more successful, some patients complain of excessive glare or fluctuating vision, especially during the first few months after the surgery.
One of the problems with the RK technique is that the final result depends on how the patient heals, and no two people heal exactly the same way.
Another point to consider: Because of their nearsightedness, some patients over age 40 are able to read and do other close work without glasses. But when they have RK, they usually lose that ability to read without glasses. They have traded their good reading vision for good distance vision. Of course, they can still read, but now only with glasses.
Alternatives to Radial Keratotomy
For several years before Dr. Fyodorov introduced RK, Dr. Jose Barraquer of Bogota, Colombia, had been reshaping eyes with a group of delicate and precise surgical procedures known as keratophakia and keratomileusis. While Dr. Fyodorov's RK technique is best suited to people with a small or moderate amount of nearsightedness, Dr. Barraquer's procedures work best for people with a high degree of hyperopia (farsightedness) or myopia.
His procedures, however, require both great surgical expertise and computer-controlled equipment. That's part of the reason the techniques have not caught on in North America. They are exceedingly difficult to master.
Another technique, called epikeratophakia, has also gained some attention. And an even newer procedure, called laser corneal sculpting, is also being investigated.
Let's look at each one separately.
Keratophakia is used to correct a hyperopic, or farsighted, person's vision, usually after cataract surgery. Instead of implanting an intraocular lens, a donor cornea is obtained from an eye bank and then rapidly frozen. This frozen cornea is then placed on a lathe and precisely cut to form a small lens called a lenticule. The lenticule has to be cut in just such a way that it overcomes the patient's farsightedness.
Once the lenticule has been made, the front half of the patient's own cornea is shaved off with a sharp intrument known as a microkeratome. This functions much like a carpenter's plane used to shave or smooth a piece of wood.
The lenticule is then placed over the remaining cornea.
After that, the "shaving" of cornea that was removed from the eye with the microkeratome is replaced over the lenticule and sewn on using extremely fine nylon sutures.
What you have now could be termed a "corneaburger," with the donated and sculpted lenticule in the middle and the two halves of the patient's own cornea serving as the "bun."
If your reaction to this procedure is amazement, read on.
The human cornea is only 1/2 millimeter thick, about the thickness of a fingernail. It is also curved. The cut splitting it has to be perfect.
The focusing power of the lenticule also has to be perfect if the patient is to see correctly when it's all over.
Several hundred different steps are involved in the operation, and each one of them must also be perfect. Aside from the surgical team, an additional team is required just to make sure that the computerized equipment is working correctly.
Although many surgeons who have studied keratophakia have given up on it in favor of lens implants and other refractive surgical procedures, the results are reportedly good when all the equipment and team members function perfectly. Research is still being done on the procedure, and new developments could make it easier and safer.
A Lenticule with Less Fuss?
Lenses can be made from a wide variety of substances. That's also true for lenticules—the tiny but vital lens elements employed in keratophakia.
While donor corneas are the usual source, research is being conducted with lenses made of a tongue twister of a compound known as hydroxyethylmethacrylate, the plastic material used for making soft contact lenses. The search is continuing for the best plastic and the most accurate way of cutting it to form suitable artificial lenticules.
If you thought keratophakia was tricky, wait until you learn about keratomileusis. While keratophakia can be used only for farsightedness, keratomileusis can be used on both farsighted and nearsighted eyes.
In this procedure, the cornea is once again shaved with a microkeratome. But this time the cornea in question is the patient's own. Instead of sculpting a cornea from the eye bank to serve as a lenticule, the top half of the patient's own cornea is frozen and carved. Once it is carved, it is sewn back on.
There are a number of reasons why keratomileusis is trickier than keratophakia. If the doctor makes a sculpting mistake, the patient has lost half a cornea. While it can be replaced with a donor cornea, the transplant might be rejected. Even if it isn't, it will never be as stable as the patient's own cornea.
Also, in keratophakia, the donated cornea can be frozen and prepared in advance so it is ready as soon as the patient's own cornea has been shaved. But in keratomileusis, the top half of the patient's cornea has to be frozen and carved while the patient is on the table under anesthesia. This just compounds the pressure under which both the surgeon and the rest of the surgical team have to operate.
Epikeratophakia is similar to keratophakia in many respects, but there are a few important differences. Here's what's involved.
First, a donor cornea is obtained. The cornea is frozen and then ground to the right prescription to make a lenticule.
Second, a circular groove is cut into the patient's peripheral cornea, outside the part of the cornea that's looked through. Once the eye has been cut, the surface layer of cells—the epithelium—covering the cut-around area is removed from the cornea.
Third, the lenticule is placed on the denuded surface of the cornea and the edges are tucked into the peripheral groove. The lenticule is then sewn into place with extremely fine nylon sutures.
After several days, the patient's epithelium will grow over and cover the lenticule, helping to hold it in place after the sutures are removed.
This procedure has certain advantages over keratophakia.
Epikeratophakia has been used mainly for the correction of farsightedness after cataract operations, especially when there is some risk associated with implanting an intraocular lens. It has also helped infants with congenital cataracts who cannot be fitted with contact lenses. For them, epikeratophakia can be both a sight-saving procedure and an amblyopia preventive.
Epikeratophakia has also been used for keratoconus, a condition in which the cornea is very distorted. Epikeratophakia helps round out the cornea in some cases.
So far, even though epikeratophakia looks promising, it has not been around long enough for long-term results to be measured. There are a number of areas in which complications could develop.
One possible concern is the fact that the corneal "sandwich" produced by the procedure is rather thick. We don't yet know what the long-term effects of this will be on the endothelium, the inner layer of the cornea that maintains the cornea's clarity.
It is also difficult to make a perfect groove in the surface of peripheral cornea with the instruments that are currently available. These instruments will have to be refined and improved so that ophthalmologists can perform this operation with greater accuracy.
Laser Corneal Sculpting
Unlike keratophakia or keratomileusis, which require temporarily removing or replacing at least part of the cornea, in laser corneal sculpting your cornea never leaves your eye.
Instead, a computer-controlled laser sculpts or reshapes your cornea. And instead of requiring hours on the operating table and days in the hospital, once all the mapping and measuring is done, the actual procedure takes about 10 seconds in your doctor's office.
The key to the procedure is the laser and the computer that operates it. The eye is first mapped and the surgeon determines exactly what parts should be treated. These data are fed to the computer, which prepares the different "shots" the laser will fire. Each nearly overlapping rapid-fire shot is aimed in advance to neatly clip off a different piece of corneal tissue.
You then sit facing the machine and are "centered" on the laser. It starts, and for the 10 seconds it takes, it sounds like a machine gun going off.
If you flinch, cough, blink, sneeze, or make any other move while the procedure is in progress, the laser will automatically shut off. Because the entire procedure is being videotaped, the video image of what the eye looked like just before the laser was interrupted is frozen and saved. That way the laser can pick up exactly where it left off once you have been repositioned in front of the machine.
Corneal sculpting is designed to work for both nearsighted and farsighted people, people with astigmatism, and those who have had their cataracts removed but have not had an intraocular lens implanted.
Proponents say it could replace many of the other surgical techniques. One way or another, it seems that Dr. Fyodorov's prediction that "someday we will build monuments with our useless eyeglasses" may be destined to come true.
A Costly, Risky Decision
While the nonsurgical procedures that can be used to improve a person's vision are basically limited to glasses and contact lenses, the number of surgical approaches and techniques seems to increase every year.
The entire field of refractive surgery is a new and still somewhat controversial area of ophthalmology. Unlike comeal transplants and other eye operations performed soley for medical reasons, many of these new procedures raise an entirely different issue: What constitutes necessary—and unnecessary—surgery?
Because procedures like radial keratotomy, keratophakia, keratomileusis, epikeratophakia, and laser comeal sculpting are so expensive, the question of affordability is extremely important. While insurance companies may pay for some of these procedures in some situations, they won't in others. That can put sharper vision out of the price range of many people.
People who are considering having one of these operations should literally go out and do their own research, talking to a number of different doctors about benefits, risks, and costs, and carefully making up their own mind before risking their eyes.