As Far as the Eye Can See

Source: FAA Safety Briefing - Mar/Apr 2021
By: Leo M. Hattrup, M.D., FAA Medical Officer

Sight is the most important sense we use in aviation. From pre-flight to taxi, and in all aspects of flight, sight is key — especially when it comes to “seeing” and avoiding any risks or conflicts.

Visual standards for Class I and II airman medical applicants require having, or correcting to, 20/20 far vision and 20/40 near vision in each eye separately. Class III medical applicants must have or correct to 20/40 vision, near and far. Color vision adequate for the safe performance of aviation duties is necessary for all classes. Pilots who choose an alternate pathway from FAA medical certification can fly using the limitations on their driver’s license. These visual standards can be as low as 20/50 in some states and many have no color vision requirement.

Consider the current standards as minimums to ensure safety. Better vision increases the time one has to react. Consider two aircraft five miles apart approaching each other head-on at 125 knots each. The closure speed of 250 knots means they will meet in 72 seconds. Spotting an aircraft head-on from five miles away can be challenging. The cues available at five miles for someone with 20/20 vision are not available until 2½ miles — a closure time of 36 seconds — if your vision is 20/40. How often do we find ourselves heads-down looking at a map/tablet, checking an approach plate, or programing the GPS? What if the other pilot is also heads down? The big sky theory sounds good, but there are many choke points and no mandated altitude separation at or below 3,000 feet above ground level. Try timing how long it takes you to perform routine cockpit tasks (with a safety pilot, of course). It could be an “eye-opener.”

The FAA strongly encourages all pilots to obtain their best corrected vision. We allow use of spectacles or contact lenses in general. However, we do not permit monovision lenses (i.e., one lens corrects near and the other far vision) or contacts that only correct for near vision. Bifocal or multi-focal contact lenses are acceptable. We generally permit other surgical corrections, although after monovision surgery you will need a six-month stabilization period before applying for a medical flight test and statement of demonstrated ability. Earlier approval is possible if you wear corrective lenses. So it’s a good idea to discuss any proposed changes to your current (approved) method of correction with your aviation medical examiner (AME) first.

Your examiner checks your color vision using an approved testing device at the time of the examination. Those who do not pass this testing can opt for an operational medical test. This includes correctly identifying the colors on a signal light test and reading a sectional chart. Historically, we considered color vision adequate for aviation if the pilot passed the operational test. However the current aviation environment is much more color rich, which creates challenges for someone with color deficiency. Even if they can interpret the displays, they may take longer to do so and risk is increased. Even if you have been cleared by the FAA, if you do have a color deficiency, try reading a sectional chart in different light conditions and the aircraft color displays on the ground, and then have an instructor check you again in flight. Note that while color deficiency is typically an inherited condition, it can also be caused by certain medications and diseases. There is no cure for a color deficiency. Glasses advertised as a “cure” actually filter out some light wavelengths. They can improve contrast, but we prohibit their use because they can block some colors on a sectional chart and colored displays.

One final thought. If you need glasses or contacts, carry a spare pair. Glasses break and get lost and contacts fall out. Having a backup just might save the day, and your flight.

Leo M. Hattrup, M.D., received a bachelor’s degree from Wichita State University, a master’s in public health from Harvard University, and a doctorate from Vanderbilt University. He is retired from the U.S. Air Force in which he spent the majority of his career in aerospace medicine. He is board certified in aerospace and occupational medicine. He is a certificated flight instructor and enjoys flying airplanes, helicopters, and gliders.