Medical Briefing: Perfect Vision

From the earliest days of flying, it became apparent that pilots had to have the best possible vision. Military aviation in World War I found that pilots who didn?t have 20/20 vision often crashed long before they entered aerial combat. Pilots needed to wear goggles because the engines of their open cockpit biplanes sprayed them with oil. Because goggles then didn?t accommodate glasses, the pilots needed uncorrected 20/20 vision.

When the forerunner of the FAA issued the first medical regulations in 1926, this World War I vision standard became the gospel. And for professional pilots it remained essentially unchanged for 60 years ? long after aircraft had closed cockpits and jet, rather than rotary piston power. Today, the FAA issues medical certificates to pilots whose vision is 20/20 ? with or without correction. This is for all classes of medical certificates, including first class. To get a third-class medical your distant vision must be at least 20/40 or better with or without correction. Near vision requirements, what you can see at a distance of 16 inches (and 32 inches if you?re older than 50 and applying for a first- or second-class medical), also must be 20/40 or better. This means you can wear contact lenses or trifocal glasses, and if they correct your vision to the required minimums, you meet the FAA?s vision requirements.

But some people don?t like to wear glasses or contact lenses. As a result, surgical procedures to correct a person?s vision have become popular. Today, we have three such procedures, ?radial keratotomy? (RK), ?photorefractive keratectomy? (PRK), and a variation of PRK called ?LASIK.? The last two use a laser beam to reshape the front surface of the cornea and change its magnifying power. These procedures enable 80 to 90 percent of all patients to attain 20/20 vision without glasses or contacts. Let?s look at what this is all about.

First, what is 20/20 vision? In essence, it says that you see at 20 feet what a ?normal? person sees at 20 feet. The target is usually a series of block letters whose bars comprise six arc-seconds, a measure of refractive resolving power. A ?normal? person is only a statistical statement. In reality, some humans have extraordinary eyesight. Perhaps the most famous is Chuck Yeager, who could see 20/10, that is he could see at 20 feet what a ?normal? person could see at 10 feet. In other words, he could resolve targets that are three arc-seconds across, half the size of the target described above. Conversely, in most states it?s legal to drive if your vision is only 20/40, or you are able to see targets that are 12 arc-seconds across.

Three components determine how well you see. First is the eye?s focusing power, which is mostly concentrated in the cornea, or outermost clear portion of the eye. The crystalline lens, located just behind the pupil, provides additional focusing power.

Second is the nature of the nerves in the eye?s retina. How closely packed these nerves are in the retina?s center determines the eye?s central visual acuity. Some people are blessed with better quantity and quality of these nerves than others. There?s nothing you can do about this ? it?s a genetic deal.

Finally, there?s the nature of your brain. It must be able to integrate the information your eyes see. A perfectly refracted eye whose information does not register in the brain will be blind, a condition called ?amblyopia.? Occasionally, a child is born with a ?lazy eye,? where the brain ignores the information from one eye and only recognizes information from the other eye. Unless the brain is retrained while the child is young, this will lead to amblyopia, or functional blindness on a neuralgic basis. There?s no way to correct this with lenses or anything else to the eye because the problem is within the brain itself.

Most people, however, have a slight degree of error in the way their eyes focus. People who read a lot tend to be slightly myopic ? nearsighted. There also is a strong genetic component that determines whether someone becomes nearsighted or farsighted.

Near and far sightedness can be corrected surgically. The original procedure, now obsolete, is called radial keratotomy. The physician makes a star-shaped pattern of cuts in the cornea, leaving the center part clear. But these cuts cause scars to form and change the shape and curvature of the eye. This procedure took a tremendous degree of skill and experience. Even so, it had a significant rate of failure and complications.

Today, two new surgical procedures use the excimer laser to precisely reshape the cornea. In PRK (photoreactive keratectomy), the laser burns off portions of the cornea to resculpture and change its shape. The laser uses a special frequency so the cornea absorbs all of its energy. The procedure results in some discomfort and problems seeing for a few weeks.

A variation of PRK called ?LASIK? (laser assisted in situ keratomileusis) is now the standard procedure. The surgeon peels off a thin outer layer of the cornea (under anesthesia, of course), uses the laser to reshape the middle layer, and then puts the outer layer back in place. The results are astonishing. In 24 hours, the person may be essentially pain-free and able to see without glasses. That is the good news.

Here is the bad news. First, is the cost. LASIK runs around $2,000 per eye, and because it?s considered a cosmetic procedure, insurance often doesn?t cover it. Second, is occasional complications.

Sometimes, the surgeon doesn?t cut the peeled outer layer to the right depth. This merely necessitates replacing the layer, postponing the surgery for a few weeks, and then repeating the procedure. Another complication occurs when the middle layer isn?t reshaped out far enough. This causes people to see a bit of a ring or ?flare? effect, particularly at night. Some patients complain of glare when they look at lights, such as approach lights while they land an airplane. This is usually a nuisance. Occasionally, more serious problems can also occur such as perforation of the eye and subconjunctival hemorrhages.

The cornea is quite thin, only about 0.5 mm at its center. Therefore, only a skilled eye surgeon should perform the surgery. Despite the fact that the surgeon has to learn how to do this procedure, I would certainly inquire as to how many procedures he (or she) has performed. At least 500 cases is good, and several thousand is much better. Not every eye surgeon does this procedure.

As with all types of surgery, serious and rare complications can arise. If you are considering this procedure, make sure your surgeon explains them to you fully so you understand the risks as well as the benefits. Not wearing glasses, which is achieved by 90 percent of LASIK patients, is relatively benign compared to the risks of serious vision loss, a complication that may occur in one out of every 2,000 or 3,000 cases.

Your life goals are another concern. The FAA will issue a medical certificate so long as your corrected vision is 20/20 or better. And, yes, the FAA will certify you after a successful eye surgery. In fact, I have several patients who fly for major airlines. If the pilot holds a valid medical certificate, the airlines cannot reject him because of eye surgery.

The military, however, doesn?t follow the FAA regs. If you hope to fly for the military, or NASA, eye surgery is not for you. The military checks all pilot applicants, and traces of refractive eye surgery are easy to detect. The same goes for active military pilots. If they have eye surgery, their flying days are over, and they can be discharged instead of being transferred to non-flying duties. The military has its reasons. The prime one is that refractive surgery permanently weakens the eye. A blow to the eye that might be a nuisance to an unoperated eye can become a catastrophic rupture after this surgery.

Should you have eye surgery? It?s a personal decision, but you should weigh the benefits and the risks carefully. Remember, this surgery cannot be undone. Tens of thousands of Americans have had this surgery and are very happy with it, but few of them have the goal of becoming a professional pilot. For those of us in aviation, the stakes are higher. The choice is yours.