by Dr. Bill Blank, M.D.
Senior Aviation Medical Examiner
© Copyright 2024. All rights reserved!
Published in Midwest Flyer Magazine June/July 2024 Digital Issue
Our eyes are one of our most important sensors. They provide us with important information about our visual environment. Among other things, this includes detail, side vision, shape, depth perception and color discrimination. Our color vision ability is innate. We are born with it. It does not change during life unless age, disease or medication side effects intervene. Color vision enables us to identify colors and discriminate shades. It can be used to give us information. This can be in traffic signals, on computer screens, aircraft instruments, to attract our attention in advertising, art, etc.
How color vision works is fascinating. It starts in the retina in specialized cells called “cones” because of their shape. The cones contain photosensitive pigments which start the process of converting the light energy into electrical signals which make their way to the brain. Different cones contain different pigments which respond maximally to different colors of light. Some peoples’ cones contain abnormal pigments which cause that person to perceive some shades differently, compared with someone with normal cone pigments. People with abnormal cone pigments are sometimes called color blind. This is a misnomer. Color deficient is a better term. They do not see the world in black and white. They see colors. They see the sky as blue and the grass as green. People with certain defects would have trouble, for example, differentiating between dark red and dark green.
From a functional point of view, there are two-color processing systems: red-green and blue- yellow. Defects can occur in either system. In both cases they are inherited. In aviation we are most concerned about pilots with abnormalities in the red-green system because these colors are frequently used in aviation. When the aviation system was designed, no thought was given to adapting to the needs of people with red-green deficiencies. The idea was to weed them out. Back then glasses weren’t permitted for professional pilots either. The same thing occurred in the selection of the colors used on sectional charts. I sometimes joke that the tower light gun is the “modern” equivalent of smoke signals. When light signals were introduced, cell phones hadn’t been invented. Cell phones were becoming popular by the mid-1980s.
The color defects I have discussed are inherited. The red-green defect is inherited from your mother. It is generally seen in males. In most cases ladies don’t demonstrate it. They would need to inherit the defect from both parents to demonstrate it clinically. In all of my years as an ophthalmologist, I have only seen one lady with it. In people of northern European extraction, the incidence is approximately 8%. It is uncommon in people of African or Asian heredity. People with blue-yellow defects are extremely rare. So far, it has not been shown to have any aeromedical significance.
I wrote this article because I suspect the FAA is about to change how and when applicants for flight physicals need to have their color vision tested. I don’t want to speculate on the details. From what I hear, it will be a mixed bag. I wouldn’t be surprised if it causes an uproar. This may become a subject for another article.
Until next time, happy flying!
EDITOR’S NOTE: Columnist William A. Blank is a physician in La Crosse, Wisconsin, and has been an Aviation Medical Examiner (AME) since 1978, and a Senior AME since 1985. Dr. Blank is a retired Ophthalmologist, but still gives some of the ophthalmology lectures at AME renewal seminars. Flying-wise, Dr. Blank holds an Airline Transport Pilot Certificate and has 6000 hours. He is a Certified Flight Instructor – Instrument (CFII) and has given over 1200 hours of aerobatic instruction. In addition, Dr. Blank was an airshow performer through the 2014 season and has held a Statement of Aerobatic Competency (SAC) since 1987. He was inducted into the Wisconsin Aviation Hall of Fame in 2021.
DISCLAIMER: The information contained in this column is the expressed opinion of the author only, and readers are advised to seek the advice of others, including their own AME, and refer to the Federal Aviation Regulations and FAA Aeronautical Information Manual for additional information and clarification.
