Safe aircraft operation requires unimpaired vision, and visual fatigue can reduce pilot performance if allowed to go untreated or prevented. Many factors affect eye fatigue, including long flights, flights in bad weather and operations at high altitudes with exposure to harsh uv rays.
The physiological effect of eye fatigue decreases the ability of flight crew members to function normally. Combined with excessive optical stimulation or prolonged visual exertion, fatigue of the visual system may occur, affecting both the eye and the eye muscles creating “visual fatigue” and the inability of the pilot’s visual system to maintain efficient and effective functioning.
Sustained Visual Monitoring
In and of itself sustained visual monitoring of aircraft instruments during instrument flight operations, or operations in haze or cloudy conditions, bright sunlit conditions and variable lighting conditions can result in increased visual demands and result in eye fatigue. Should a significant malfunction of the visual system occur during flight could result in transitory ocular motion impairment, causing recession of focusing, slowed or delayed focusing, impaired extraocular muscle balance and the recession of the convergence and divergence near point.
Symptoms And Signs Vary
Symptoms of eye fatigue include a burning sensation in the eye, scratchy, dry or painful eyes. Other symptoms include excessive tearing, blurred vision, double images, “heavy” eyelids and frontal headaches are common indications of visual fatigue.
Subtle Operational Implications
The most important result of visual fatigue is the possible inadequate perception and/or interpretation of in-flight visual information required for safe aircraft operation. With the development of multi-function displays in aircraft instrument panels visual monitoring becomes increasingly important to pilots.
Under certain conditions visual fatigue may, in fact, hamper the transfer of vital flight information from instrument displays to the pilot, resulting in inefficient or unsafe operation of the aircraft.
Prevent Rather Than Treat
The use of adequate corrective lenses and proper sunglasses is essential. Lenses should be kept free of scratches and kept clean. The avoidance of self-imposed stressors such as alcohol, tobacco, drugs and sleep loss are important preventative measures.
Eyes can be rested by varying the viewing distance every few seconds or minutes. Pilots should take a 15 minute break every 1-2 hours of continuous work.
Sunglasses for pilots should be high quality, well constructed, non-polarized and easy to use with scratch resistant lenses which block most ultraviolet light. Learn more about proper sunglasses at Pilot Sunglasses: Beyond the Image.
Until next time keep your wings straight and level Hersch!
Higher, ever higher.
“Arriba, siempre arriba”
— Georges Chavez, last words after crashing his Bleriot airplane on his trailblazing flight over the Alps, September 1910. His words became the motto of the Peruvian Air Force.
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