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Aviation Safety - Facts About Vision You Need To Know

by John M. White |

Contact Lenses

Use of contact lenses has been permitted to satisfy the distant visual acuity requirements for a civil airman medical certificate since 1976. However, monovision contact lenses, a technique of fitting older patients who require reading glasses with one contact lens for distant vision and the other lens for near vision, ARE NOT ACCEPTABLE for piloting an aircraft. Use Of Contact Lenses By Pilots The use of a contact lens in one eye for distant visual acuity and a lens in the other eye for near visual acuity is not acceptable because this procedure makes the pilot alternate his/her vision; that is, a person uses one eye at a time, suppressing the other, and consequently impairs binocular vision and depth perception. Since this is not a permanent condition for either eye in such persons, there is no adaptation, such as occurs with permanent monocularity. Monovision lenses, therefore, should NOT be used by pilots while flying an aircraft.

The Eyes Have It

As a pilot, you are responsible to make sure your vision is equal to the task of flying—that you have good near, intermediate, and distant visual acuity because:
  • Distant vision is required for VFR operations including take-off, attitude control, navigation, and landing;
  • Distant vision is especially important in avoiding midair collisions Near vision is required for checking charts, maps, frequency settings, etc.;
  • Near and intermediate vision are required for checking aircraft instruments.
Learn about your own visual strengths and weaknesses. Changes in vision may occur imperceptibly or very rapidly. Periodically self-check your range of visual acuity by trying to see details at near, intermediate, and distant points. If you notice any change in your visual capabilities, bring it to the attention of your Aviation Medical Examiner (AME). And, if you use corrective glasses or contacts, carry an extra pair with you when you fly. Always remember: Vision is a pilot’s most important sense.

KEY POINTS

  • The sharpest distant focus is only within a one-degree cone.
  • Outside of a 10° cone, visual acuity drops 90%.
  • Scan the entire horizon, not just the sky in front of your aircraft.
  • You are 5 times more likely to have a midair collision with an aircraft flying in the same direction than with one flying in the opposite direction.
  • Avoid self-imposed stresses such as self-medication, alcohol consumption, smoking, hypoglycemia, sleep deprivation, and fatigue.
  • Do not use monovision contact lenses while you are flying an aircraft.
  • Use supplemental oxygen during night flights above 5,000 ft MSL.
  • Any pilot can experience visual illusions. Always rely on your instruments to confirm your visual perceptions during flight.
It was interesting to me as I listened to NPR today when they were talking about what we see and what we THINK we see. They gave an example of where they would watch commercial airline pilots who were taking recurrent training in a simulator using heads-up displays, and the researchers would introduce another aircraft directly in the pilot's field of view when landing. 30% of the time the pilots never saw the other airplane! Knowing about and understanding our vision is critical as pilots. Take the time to read all of these posts and understand how important vision is to your safety and the safety of others. And remember, now that summer is here you need to protect your eyes against harsh sunlight when flying your airplane, so be sure and carry a good pair of Randolph aviator sunglasses with you and keep them handy. In our next article we will learn more about protecting a pilots eyes and preserving his most valuable sensory asset - his eyes. Until next time keep your wings straight and level Hersch! JetAviator7 I fly because it releases my mind from the tyranny of petty things . . . — Antoine de Saint-Exupéry ps: Don't forget to sign up for our newsletter "All Things Aviation" here!

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