Sunglasses help safeguard a pilot’s most important sensory asset — vision. A quality pair of sunglasses is essential in the cockpit environment to optimize visual performance. Sunglasses reduce the effects of harsh sunlight, decrease eye fatigue, and protect ocular tissues from exposure to harmful solar radiation. Additionally, they protect the pilot’s eyes from impact with objects (i.e., flying debris from a bird strike, sudden decompression, or aerobatic maneuvers). Sunglasses can also aid the dark adaptation process, which is delayed by prolonged exposure to bright sunlight.

The American Optometric Association recommends wearing sunglasses that incorporate 99 – 100% UVA and UVB protection. Fortunately, UVC, the most harmful form of ultraviolet radiation, is absorbed by the atmosphere’s ozone layer before it reaches the Earth’s surface. Some scientists believe, however, that depletion of the ozone layer may allow more ultraviolet to pass through the atmosphere,2 making 100% ultraviolet protection a wise choice when selecting eyewear.

TINTS. The choice of tints for sunglasses is practically infinite. The three most common tints are gray, gray-green, and brown, any of which would be an excellent choice for the aviator. Gray (neutral density filter) is recommended because it distorts color the least. Some pilots, however, report that gray-green and brown tints enhance vividness and minimize scattered (blue and violet) light, thus enhancing contrast in hazy conditions.

For flying, sunglass lenses should screen out only 70 - 85% of visible light and not appreciably distort color. Tints that block more than 85% of visible light are not recommended for flying due to the possibility of reduced visual acuity, resulting in difficulty seeing instruments and written material inside the cockpit.

POLARIZATION. Polarized lenses are not recommended for use in the aviation environment. While useful for blocking reflected light from horizontal surfaces such as water or snow, polarization can reduce or eliminate the visibility of instruments that incorporate anti-glare filters. Polarized lenses may also interfere with visibility through an aircraft windscreen by enhancing striations in laminated materials and mask the sparkle of light that reflects off shiny surfaces such as another aircraft’s wing or windscreen, which can reduce the time a pilot has to react in a “see-and-avoid” traffic situation.

PHOTO CHROMIC. Glass photo chromic lenses (PhotoGray® and PhotoBrown®), like their plastic counterparts (Transitions®), automatically darken when exposed to ultraviolet and become lighter in dim light. Most of the darkening takes place in the first 60 seconds, while lightening may take several minutes. Although most photo chromic lenses can get as dark as regular sunglasses, i.e., 20% light transmittance in direct sunlight, warm temperatures (>70°F) can seriously limit their ability to darken and reduced ultraviolet exposure in a cockpit can further limit their effectiveness. In addition, the faded state of photo chromic glass lenses may not be clear enough to be useful when flying in cloud cover or at night.

FRAMES. The selection of sunglass frames is probably more a matter of personal preference than lens material or tint. The frames of an aviator’s sunglasses, however, must be functional and not interfere with communication headsets or protective breathing equipment. Frame styles that incorporate small lenses may not be practical, since they allow too much visible light and ultraviolet radiation to pass around the edges of the frame. A sunglass frame should be sturdy enough to take some abuse without breaking, yet light enough to be comfortable. An aviator’s sunglasses should fit well so that sudden head movements from turbulence or aerobatic maneuvers do not displace them. Finally, use of a strap is recommended to prevent prescription sunglasses from being accidentally dislodged, or a necklace chain can be used to allow them to be briefly removed and subsequently replaced.

SUMMARY. While adding to the mystique of an aviator, sunglasses protect a pilot’s eyes from glare associated with bright sunlight and the harmful effects from exposure to solar radiation.

Lenses for sunglasses that incorporate 100% ultraviolet protection are available in glass, plastic, and polycarbonate materials. Glass and CR-39® plastic lenses have superior optical qualities, while polycarbonate lenses are lighter and more impact-resistant.

The choice of tints for use in the aviation environment should be limited to those that optimize visual performance while minimizing color distortion, such as a neutral gray tint with 15 to 30% light transmittance.

Polarized sunglasses are not recommended because of their possible interaction with displays or other materials in the cockpit environment.

Since sunglasses are an important asset, whether or not refractive correction is required, careful consideration should be used when selecting an appropriate pair for flying.

The technology associated with ophthalmic lenses is continually evolving, with the introduction of new materials, designs, and manufacturing techniques.

Aviators should consult with their eyecare practitioner for the most effective alternatives currently available when choosing a new pair of sunglasses.