The Latest on LASIK

About half of all pilots in the United States need some form of vision correction, such as contact lenses or glasses, to meet medical certification standards. But now pilots with imperfect vision who want to fly without corrective lenses have more options than ever, thanks to recently approved advances in laser corrective eye surgery.

Since the Food and Drug Administration (FDA) first approved laser corrective eye surgery in 1995, more than 10 million people, including more than 11,000 pilots, in the United States have undergone the surgery with the goal of seeing better. And with the recent FDA approval of a wavefront-guided system for customized refractive surgery, pilots can hope for even better outcomes.

Vision questions?

AOPA's medical certification specialists communicate with the FAA on an almost daily basis to provide the most current information to members about pilot medical certification. In addition, the Web site (www.aopa.org), includes an entire medical area that contains valuable information about many of the most common medical issues affecting pilots. Vision questions are among the most frequently asked, and the Web site has several subject reports dealing with FAA certification policy. The index for all medical subject reports can be found online. If you have questions about any medical certification issue that isn't answered on the Web site, call the medical certification specialists at 800/872-2672. — Gary Crump

Before getting into the new technology, let's first review the basics about laser corrective eye surgery, also called refractive surgery. Remember that a third class medical certificate requires at least 20/40 vision in each eye for distant vision and for reading. A first- or second class medical certificate requires 20/20 vision in each eye at distance and 20/40 in each eye for reading and intermediate distances of 32 inches. A pilot who has had refractive surgery and meets the FAA vision requirements no longer needs the limitation requiring corrective lenses on his or her medical certificate. In most instances, older pilots still need glasses to meet the near- and intermediate-distance vision requirements.

LASIK surgery

The most commonly performed type of corrective eye surgery is LASIK, or laser in-situ keratomileusis. This procedure involves the use of an excimer laser — a laser that uses a combination of argon and fluorine gases to produce a specific wavelength of light — to permanently alter the shape of the clear front covering of the eye, the cornea. The laser ablates, or vaporizes, part of the cornea, changing its shape and the refractive, or focusing, power of the eye. LASIK may be used to correct myopia (nearsightedness), hyperopia (farsightedness), astigmatism (irregularly shaped cornea), or a combination of these (for example, myopia with astigmatism). Presbyopia is the normal loss of the ability to see clearly at close distances that begins after age 40 and is most commonly corrected with reading glasses or bifocals. Presently, LASIK cannot correct both distance vision and presbyopia in the same eye, although this is being investigated in clinical trials. In other words, a patient who already needs reading correction can have LASIK to improve distance vision, but usually this does not eliminate the need for reading glasses.

Vision results today are quite good with laser refractive surgery, and for the majority of LASIK patients the surgery improves vision. Results tend to be best for patients with mild or moderate myopia. The vast majority of patients achieve at least 20/40 vision and many reach 20/20 vision. Most patients are very happy with their surgical outcome. However, LASIK still cannot provide perfect vision for every patient and as many as 10 percent of patients have some visual problems or side effects after surgery. This also means that even after surgery some pilots require correction with glasses or contact lenses to meet the vision requirements for their class of medical certificate.

Only a very small percentage of patients permanently lose vision after laser corrective surgery. On the other hand, a refractive surgery patient may end up with 20/20 vision and still be unhappy with the way he sees. Common complaints after LASIK surgery include annoying glare from lights, halos around lights at night, and poor vision in dim lighting conditions. Such visual aberrations after LASIK can cause problems for the pilot in certain aviation environments, such as when flying at night or in marginal VFR or IFR conditions, even though his vision may measure a perfect 20/20 in the doctor's office. Usually these visual complaints improve within several months after surgery, but occasionally they are significant enough to interfere with normal activities. As an example, a recent highly publicized case involved a commercial airline pilot who obtained 20/15 vision after LASIK surgery but had to end his flying career because of disabling night-vision difficulties.

Wavefront technology

LASIK is not entirely risk-free, but newly approved technologies may further decrease the likelihood of complications. One of the latest developments in refractive surgery is wavefront technology. A wavefront-guided LASIK system allows the corneal laser ablation (vaporization and shaping) to be customized for each patient, possibly leading to better individual vision outcomes.

But what's a wavefront anyway? A perfect wavefront emanates from a light source with a flat surface. When performing wavefront analysis of the eye, a light source (the wavefront) passes through the layers of the eye (tear film, cornea, natural lens, and fluids in the eye) to the retina in the back of the eye. Irregularities in the wavefront are caused by each of the components of the eye as the light rays pass through it. The now-distorted wavefront is measured as it again emerges from the eye. A wavefront sensor maps out the aberration or distortion profile of the entire eye, providing a fingerprint pattern specific to each individual eye. Even subtle distortions and imperfections are measured.

The excimer laser is then programmed to perform a customized ablation of the cornea based on the information received from the wavefront sensor. The cornea is thereby reshaped very precisely to eliminate most aberrations of the eye, theoretically resulting in perfect vision.

In conventional LASIK, corneal topography is used to determine the laser ablation profile. Corneal topography provides information about the curvature of the cornea but does not map out distortions caused by other parts of the eye through which light must pass. Wavefront-guided refractive surgery provides a new level of detail and accuracy not previously possible. Surgeons are now able to treat a much broader group of patients, improving not only the level of vision but also reducing the side effects. By correcting for all aberrations in an eye, wavefront technology has the potential to allow patients to achieve "super normal" vision, or vision that is better than 20/20. Not only are a high percentage of patients reaching 20/20 vision, but with the new technology many achieve levels of vision between 20/15 and 20/10. Perhaps more important, conventional LASIK surgery frequently causes a type of aberration that is responsible for the night-vision problems that may occur after corrective laser surgery. Wavefront-guided LASIK has the ability to correct not only natural optical aberrations of the eye but also the aberrations routinely induced by laser surgery. As a result, the incidence of night-vision difficulties after laser surgery should be reduced. Patients who have had conventional LASIK in the past and who are experiencing night-
vision problems or visual symptoms may benefit from retreatment with wavefront-guided LASIK. Wavefront technology also may allow refractive surgery in some patients who are considered poor candidates for the procedure with conventional techniques.

Interestingly, wavefront technology has been used in astronomy for many years as a type of adaptive optics to remove the blurring effects of turbulence in the atmosphere on telescopic images of the heavens. This has allowed ground-based telescopes to achieve significant improvements in resolution.

The FAA has approved refractive surgery for all classes of medical certification. After surgery, once your eye doctor has verified that healing is complete, vision is stable, and there are no significant side effects or complications, you may resume flying. Typically this occurs within four weeks after surgery. The FAA requests that your eye doctor send a summary document to the Medical Certification Division in Oklahoma.

Monovision surgery

Another relatively new option for pilots is monovision correction with refractive surgery. This refers to correction of one eye for distance vision while the other eye is corrected for reading vision. Therefore, each eye separately does not meet both the near and distance vision requirements. The new FAA policy requires that pilots who opt for monovision refractive surgery use glasses to meet the near and far vision requirements while flying for six months after surgery.

When not flying, you should not wear corrective lenses to allow optimal adaptation to the monovision state. After six months, you may apply for a waiver with a medical flight test. Not everyone is comfortable with monovision correction, and it is strongly encouraged that you undergo a several-week trial period using monovision contact lenses before undergoing a permanent surgical procedure. Also, keep in mind that while vision with only one eye has been demonstrated to be safe in the aviation environment, the overall quality of vision is still better with two eyes (binocular vision) than with one eye, or monovision.

The FAA is currently considering other types of vision correction for pilots, but presently does not approve flying with monovision contact lens correction. Similarly, the FAA does not at this time approve bifocal contact lenses for use while flying.

Advances in technology are revolutionizing vision correction surgery and pilots have an ever-greater range of options for vision correction. Most LASIK patients have good results and are able to meet FAA vision certification requirements. However, no surgical procedure, including wavefront-guided refractive surgery, is entirely risk-free. When considering laser eye surgery, make certain you discuss all the risks with your eye surgeon, including the small possibility of vision loss that may end an aviation career. Refractive surgery has come a long way, but there is still much work to be done to achieve perfect vision in every patient every time.

Ingrid Zimmer-Galler, AOPA 1219980, is a vitreoretinal surgeon at Johns Hopkins' Wilmer Eye Institute. She is also a commercial pilot and CFI with instrument and seaplane ratings. She has more than 1,600 hours and owns a Beechcraft Bonanza and Piper Cub.

Gary Crump is AOPA's director of medical certification.