The Medical Certification of Civilian Pilots Fitted With Multi-Focal Contact Lenses

By Van B. Nakagawara, OD Kathryn J. Wood, CPOT
Reprinted with permission from FAA Aviation News

Nearly 50,000 Americans become presbyopic (i.e., lose their ability to focus at near distances) each day, and most must then rely on an ophthalmic appliance (spectacles or contact lenses) to see small print at close distances. This condition normally occurs when the individual reaches 40 years of age.

Civilian pilots in the United States are required to have a medical certificate issued by the Federal Aviation Administration (FAA) to legally pilot an aircraft. Medical certificates are issued for first-, second-, and third class, depending on the type of flying being done by the pilot. The medical standards for these certificates are found in Title 14 of the Code of Federal Regulations (CFR) Part 67 of the Federal Aviation Regulations (see Table 1).

Prior to 1976, civilian pilots were allowed to wear contact lenses to correct for their distant vision while flying if the FAA had issued a waiver (SODA) authorizing their use. Since December 21, 1976, Amendment 67-10 to the CFR has permitted the routine use of contact lenses to satisfy their distant visual acuity without issuance of a SODA. The prohibition against the use of bifocal or near-correcting contact lenses, however, has remained in effect for almost three decades. In December 2005, the Federal Air Surgeon approved a policy change allowing the use of bifocal/multi-focal contact lenses by civilian pilots while flying.

To receive a medical certificate from their Aviation Medical Examiner, an airman wearing bifocal/multi-focal contact lenses, while performing aviation-related duties, must submit the following information (see Table 2).

There are now more than 25 bifocal/multi-focal contact lenses available, which include both rigid and soft lenses. Therefore, from these many lenses the eye care specialist can select the lens that will give their patient the greatest probability of fitting success.

Types of Bifocal/Multi-focal Contact Lenses

There are two different types of bifocal/multi-focal contact lenses: alternating and simultaneous. Lenses that use the alternating principle are usually rigid and have a line between the distant and near sections similar to bifocal spectacles. They provide the best vision at both distances but are more difficult to fit on a patient's cornea (Figure 1).

Simultaneous vision lenses position both the distance and near portions over the patient's pupil at the same time. The individual's visual system learns to interpret the correct refractive power choice depending on how close or far they are from the object. Patients with this type of lens may experience blurred vision due to interference to the in-focus image, which is produced by an out-of-focus image. (Figure 2)

There are three types of simultaneous lens designs: concentric, aspheric, and diffractive. Simultaneous lenses can be manufactured from both soft and rigid materials.

Concentric designed lenses have t he center portion of the lens to correct for distant vision and the peripheral portion to correct for near vision, or vice versa1 (Figure 2). A blended design, such as an aspheric simultaneous contact lens, changes power gradually from the center to the edge of the lens (Figure 3). Due to the gradual change in power, correction for intermediate distances is possible. This lens reportedly corrects points of aberration in the patient's eyes, thus providing a more natural vision correction.

Diffractive lenses use a series of grooves cut into the back surface of the lens to provide near vision correction (Figure 4).  These grooves form a series of concentric rings that divide incoming light between near, intermediate, and distant images. As soon as an image is too close for distant vision, the middle focus becomes dominant; remaining in effect until the object is at a reading distance, where near focus becomes dominant. The closer the spacing between the grooves, the higher the add power.

Airmen must be aware that there are certain lenses that are not approved for use in aviation.

Bifocal/multi-focal lenses are reported to provide most patients with good visual performance (20/25 or better) at far and near distances. Depending upon the type of contact lens, some users have reported a loss of contrast sensitivity compared to spectacle use, although most individuals do not feel this significantly affects their visual performance.

The use of contact lenses may become increasingly problematic due to normal changes that often occur with age. These can include anatomical and physiological changes (e.g., flaccid eyelids, reduced tears, and diminished corneal sensitivity) and the use of medication that may alter tear production.

It has been found that spectacle correction may limit or prohibit the use of certain equipment, (e.g., night vision goggles, helmet-mounted displays, chemical protection masks). With more than 22 % of their aviators requiring some type of correction, the military has performed several studies regarding the effectiveness of contact lenses use in a variety of aviation environments.

Aircrew members who wore contact lenses in the harsh wartime environment of Desert Shield/Storm found them to be operationally superior to spectacles. However, a study that fit senior military aviators with five different types of soft bifocal/multi-focal contact lenses found that the best performing contact lens slightly reduced visual performance compared to that of bifocal glasses.

A recent study reported on the successful use of multi-focal contact lenses by pilots in the Royal Netherlands Air Force, while another U.S. Army study of Apache helicopter pilots found that multi-focal contact lenses met the visual demand s required w it h no loss of visual performance. Airmen must be aware that there are certain lenses that are not approved for use in the aviation environment, such as designer lenses that introduce color (tinted lenses), restrict the field of vision, or significantly diminish transmitted light.

In conclusion, civil airmen may now receive a medical certificate allowing them to use bifocal/multi-focal lenses while performing aviation duties. All that is required is to have the proper documentation from their eye care practitioner of the lenses' performance capabilities prior to seeing their AME. This will facilitate the issuance of a medical certificate with these ophthalmic devices.