Refractive Eye Surgery – Is It Time For The Aviator?

By R. Wilbur C. Blount, M.D. FACS, FICS

Colonel, USAFR/ANG MC CFS (Ret.)

Sport Aviation, June 1997

I. What is Refractive Eye Surgery?

Most of us are aware of the fact that there are new developments in eye surgery intended to reduce the dependence on glasses or contact lenses.

Refractive eye surgery includes several surgical techniques designed to improve the problems in focusing the eyes, also known as refractive problems. Until recently, only glasses or contact lenses could correct refractive problems.

II. What are Refractive Problems?
Light is focused, or refracted, by the cornea, the clear "window" in front of the eye. Your vision is clear if the cornea and lens combine to focus the image precisely on the retina. The retina is the inner layer of the eye that senses light, helps you see. The electrical impulses that develop are transmitted to the brain via the optic nerve.

Your vision is blurred if the cornea, lens and eye length place the image in front of the retina. This condition is known as myopia or nearsightedness. If the cornea is not round (like a basketball) and has unequal curves (like a football), the image is distorted. This distortion is called astigmatism. An eye with an astigmatism may also be a nearsighted eye, or myopic. A hyperopic eye is an eye that sees images quite clearly at a distance, but not at near. As yet, the hyperopic eye cannot be corrected easily by keratotomy or laser therapy.

III. Refractive Solutions:

Refractive problems such as myopia and astigmatism are solved by helping the eye focus the light using glasses, contact lenses or refractive surgery. Refractive surgery techniques are aimed to change the eye focus by changing the shape of the cornea in various ways.

• The surgeon may make an exact pattern of incisions along the cornea.
• The surgeon sculpts the cornea into a new shape by removing tissue with an automated blade (keratome) or laser.
• The surgeon inserts natural or manmade materials on or within the cornea to change its shape. Refractive surgery is evolving as new techniques and instruments become available.

IV. How Safe is Refractive Surgery?

Radial keratotomy is used to improve myopia by changing the curvature of the cornea. Using a microscope and microscopic instruments, the surgeon makes several deep incisions (Keratotomies) in the cornea in a radial or spoke-like pattern. The operation requires less than thirty minutes and is usually performed using only topical medications to anesthetize the cornea.

Since its introduction to North America in 1978, radial keratotomy has undergone many modifications and the predictability of the operation has improved. It had previously been accomplished in Russia for many years prior to that. Even back in the late 1930s it was pioneered in Japan before WW-II. Currently, several hundred thousand people in the U.S. have had RK. Approximately 90% of the people selected for RK could, following their surgery, pass a driver’s license exam that requires 20/40 vision or better without glasses or contacts. About 10% of the people would still need glasses or contact lenses to pass. The final visual outcome for each individual cannot be precisely predicted.

In one study of the effectiveness of RK, 64% of the people did not wear glasses or contact lenses five years following surgery. Approximately 36% did require glasses, at least for some situations. People with mild myopia have even more satisfactory results. Reading glasses may be necessary in the older patient because RK cannot alter the normal aging process of the eye.

Complications at the time of surgery are rare, but can be serious. After RK the cornea heals slowly and concerns remain because of the side effects with delayed corneal healing. There may be:

• "fluctuating vision" especially the first few months following surgery;
• a weakened cornea more vulnerable to rupture if hit directly;
• infection;
• the need for additional refractive surgery to enhance the initial procedure;
• difficulty fitting contact lenses;
• glare or star bursts around lights;
• temporary pain.

Currently, refractive surgery using the radial keratotomy technique is best accomplished on moderately myopic patients and has had a reasonable acceptance. However, the fact that star bursts may occur, a weakened cornea, and the possibility of fluctuating vision, have ruled this procedure out currently for airmen. The military services do not allow people who have undergone this procedure to enter flight training regardless of some of the advertisements in the press.

V. How Safe and Effective is Photorefractive Keratectomy?

Photorefractive Keratectomy is a process by which the excimer laser has been utilized in the past few years to correct myopia. Currently, several thousand people have had the procedure accomplished in the U. S. since its approval in late 1995. Prior to that time many U.S. citizens went to Canada where the procedure and instrumentation was approved several years before the FDA approved it for use in the United States. Authorized research studies were reviewed by the FDA and in the U.S., the excimer laser was approved for use in late 1995.

During PRK the excimer laser precisely sculpts the surface of the cornea using a visible light energy. It is hoped that this procedure will produce more stable results than RK. While not yet proven, there is hope that the procedure will be more stable than RK.

VI. The Excimer Laser:

The excimer laser was first developed by IBM to make submicron cuts in computer micro chips. In 1983 a physician patented the idea to use the laser to cut the cornea as done in RK to reduce myopia. Instead of making multiple deep peripheral cuts in the cornea, the laser was utilized to vaporize corneal tissue. The cornea itself is only 1/2 mm thick and .10 of this central thickness must be removed to eliminate most patients myopia. The excimer wavelength is well suited for corneal treatment. It does not penetrate nor does it cause adjacent tissue damage. The advantages over RK includes computer accuracy, its long term visual stability, and the strength of the eye is not altered, leaving it to withstand trauma much better than the RK procedure. The chances for infection are much less using the excimer laser. No surgical blades are used and the procedure takes approximately fifteen to twenty minutes. Eye drops are used to anesthetize the cornea. Complications during the procedure are relatively rare. In a mild form of myopia PRK and RK have similar results. The cornea should be able to withstand injury better after PRK than RK.

A common, but temporary problem after PRK is hazy vision. This usually improves several months following the procedure. Clinical trials indicate that it rarely results in permanent scarring of the cornea.

Approximately 70% of people who have PRK will have halos surrounding their vision at night. These symptoms usually decrease after six months. As with RK, most people are pleased with the results, particularly those who do not require over correction or contact lenses. The long term results and safety of PRK are unknown until research trials are completed.

VII. Should You Consider

Refractive Surgery?

You might consider refractive surgery if you:

• wish to decrease your dependence upon glasses or contact lenses;
• are free from eye disease;
• can accept the inherent risk and side effects of the procedure;
• have the appropriate refractive error. After refractive surgery some people still need glasses or contact lenses for some situations.

Refractive surgery does offer an alternative from dependence on glasses and contact lenses, however, you may not be an acceptable candidate for it. If you cannot accept the variable outcome, then you should avoid the procedure. How to correct your vision should only be determine after a thorough examination by your ophthalmologist.

If you are an airmen or if you intend to enter commercial aviation or the military, refractive surgery is not an option at the present time. If your visual acuity does not meet the minimum requirements, then having refractive surgery to bring you into the acceptance requirements for training will not be acceptable.

Those military and commercial aviators Class I and II who have undergone this procedure must acknowledge this. Having the procedure will prevent you from being hired or taken into the air force. If you enter under perjury and it is found out that you have had the procedure can be easily determined under sophisticated examination, then you will be subject to discipline and removal from the training program.

Currently, the United States Air Force, Navy, Marines, Coast Guard and Army trainees will not be accepted if they have had refractive eye surgery. It is important to be frank if you have had refractive eye surgery. Class I and II are approved by the FAA rules for commercial aviation and private pilots.

Parameters for treatment are variable, but we do know that permanent reshaping of your eye with the laser can be precisely accomplished. It is not known what the long term side effects may be.

The navy is performing a program using SEALS to determine the long term effect since their dependence on good eyesight without contact lenses and glasses is vital. After a five year follow-up we will be able to determine just how acceptable the refractive procedures are. The outcome of this study may change the rulings of the military service regarding flying personnel and refractive surgery. If you have the procedure done it is important to acknowledge this on examination during your medical history. Specifically, the FAA will issue a medical certificate by the examiner if the applicant meets the visual acuity standards, healing has been complete, visual acuity remains stable, and the applicant does not experience significant glare intolerance.

(Dr. Blount, EAA 81194, is a member of the EAA Aeromedical Advisory Council.)