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  • Eyes to the Sky

    Vision is the most important of the five senses for a pilot. In addition to mental alertness, sound judgment, and quick reflexes, vision allows the pilot to examine his or her surroundings and base crucial decisions on the information that the eye transmits to the brain. Health, fatigue, alcohol, drugs, smoking, and atmospheric conditions all contribute to eye function while in flight.
    Aviation Medicine

    Aviation medicine (also known as flight medicine or aerospace medicine) was born in the 1700s from observations made by the scientists and engineers piloting hot air balloons. Those involved in early ballooning noted that high altitude flying could cause paralysis, visual acuity and hearing loss, and eventual unconsciousness. However, it was not until WWI that serious work was undertaken by governments to test pilots for their aptitude for flight.

    Aviation medicine research focuses on several factors that affect pilots. High altitude flying can hold many dangers including hypoxia (lack of oxygen), decompression sickness (changes in air pressure), extreme cold, and G-forces (effects on the body by rapid changes of direction at high speeds).

    Aviation Goggles, c1944

    Goggles such as these were issued to early US Army aviators like Col. Thomas J. Tredici, MD. They were meant to help protect the eyes at high altitudes at a time when airplanes had little in the way of comfort for the crew.


    A man uses a large medical instrument to examine a person's eyes. The man on the right is a middle aged white man with dark hair and dark framed eye glasses. He wears a white lab coat, and he is holding a large black and silver metal instrument. He is examining the eye of the person on the left, who is wearing a blue jumpsuit and wears a strap across their lap and a snap around their head.G-forces can cause a pilot to temporarily lose vision and consciousness. To study the problem the U.S. built a number of centrifuges in the 1940s. Centrifuges create high rates of acceleration allowing scientists to study the body's reactions.

    Thomas D. Duane, MD
    A black and white photograph of an older white man wearing a suit. He has gray, salt-and-pepper hair and he wears square framed eyeglasses.One such study was conducted by Thomas D. Duane, MD in the early 1950s. Dr. Duane worked with the centrifuge in Johnsville, Pennsylvania, which was capable of producing 40 Gs of force, to study "positive blackout" or temporary blindness. Dr. Duane was able to prove that during high acceleration the ocular circulation system was being deprived of blood causing pilots to lose their sight just before losing consciousness. His research was instrumental in designing the pilot's G-suit.

    Emil G. Bethke
    An orange and red drawing of the inside of the human eye. There is a circle in the center of the drawing mimicking the optic nerve, and several thick and thin red lines, mimicking veins, are extending down into the circle.Emil G. Bethke was a medical illustrator tasked with documenting Dr. Thomas Duane’s findings. He did this with colored drawings like this example which he made by climbing into the centrifuge with the pilots. The pilots would be in a sitting position, experiencing high G-forces while Bethke would perform an ophthalmoscopy exam lying horizontally next to them. According to Duane, Bethke did this for about a week during which time he rode the centrifuge multiple times until he was able to see the changes going on inside the pilot’s eyes.
    Visual Acuity

    A black and white eye chart with multiple rows of black English letters. The top row has two large letters, and the font of the rows gets progressively smaller until the bottom row, where there are ten very small letters.Visual acuity is the measurement of how well we see, and is usually tested by having the patient read an eye chart. Pilots must have good visual acuity and rapid accommodation to judge distances accurately. Pilots must quickly focus on objects that are near, intermediate, and distant - switching easily from looking out an aircraft window to monitoring instruments or charts. Also critical to their job is good peripheral and night vision.

    Testing Visual Alertness

    A faded page of a newspaper with a black line drawing on it. There are stylized drawings of a man and a woman flamenco dancing, and a drawing of a large man kissing a small woman. The headline on the paper says: The New York Times.It is said that the U.S. government employed an unusual method of testing visual alertness. Supposedly they asked pilots to look at the drawings of the famous caricaturist, Al Hirschfeld, who was known for hiding the name of his daughter, Nina, in his illustrations. In theory, finding the hidden “NINA” in the drawing helped improve attention to detail which was critical for map reading.
    Color Vision

    A green book cover. The book has a hard cover, with gold block lettering. The cover reads: Color Blindness Test Charts, Handaya, Tokyo, Japan.Color has played an important role in aviation. Prior to the use of the radio, visual communication with pilots was necessary so airmen devised methods that involved using both symbols and colors. These methods continue today with uniforms, aircraft position lights, light-gun signals, airport beacons, approach slope indicators and chart symbols all utilizing specific shapes and colors.

    Color Test

    A large circle made up of many smaller colored circles. Most of the large circle is filled with small pink and orange circles, but there is the shape of the number 5 in the center made up of small green circles.During WWI, the Japanese Army Medical College asked Dr. Shinobu Ishihara to create a test to screen military recruits for color blindness. In 1917, he published thirty-eight plates made up of color dots in different shades with a number or line hidden within. The tests checked for both protanopia (red blindness or weakness) and deuteranopia (green blindness or weakness). Together, red-green color blindness is found in approximately 8% of men. Ishihara’s test was crucial in vetting flight personnel and was one of the first contributions of vision science to aviation.
    Spitfires & Hurricanes

    A black and white photograph of an older white man wearing a suit. He has thin white hair and a white mustache, and he wears eyeglasses and a dark suit.During WWII pilots suffered injuries from shattered cockpit canopies. Sir Harold Ridley, MD, a British ophthalmologist who treated Royal Air Force pilots in Britain during the war, saw many of these injuries. Dr. Ridley observed that the fragments did not cause infection, and the body did not reject the slivers of plastic because the acrylic was light, inert, and did not act as an irritant. The discovery led him to develop the intraocular lens (IOL).

    Supermarine Spitfire Airplane Canopy, c1938-1954

    A large clear plastic dome with a metal border. The plastic is clear, but has a lot of wear and tear, so it is somewhat opaque. The metal border has small rivets all around it.The Spitfire airplane was designed by the British and put into service in 1938. In addition to being a fighter-bomber, the Spitfire also flew photo reconnaissance missions. In the 1930s, the Spitfire was considered to be the fastest military airplane in the world. It’s windshield and canopy were made of polymethyl methacrylate (PMMA), the same plastic later used by Sir Harold Ridley, MD in intraocular lens implants.

    Intraocular Lens, c1950

    A small round plastic medical device sits on a dark red foam pad inside of a round white plastic case.This is a Ridley designed intraocular lens implant made of PMMA.