Color Vision Deficiency in Pilots

What is Color Vision Deficiency?

Color vision deficiency (CVD), commonly known as color blindness, is the inability to perceive certain colors accurately. The most frequent type is red-green deficiency, but blue-yellow deficiencies also exist. In aviation, accurate color discrimination is critical for reading instrument displays, recognizing warning lights, interpreting airport lighting, and identifying navigation signals.

Aviation Color Vision Requirements

To qualify for a pilot license, candidates must pass an initial color vision screening. If a pilot fails the standard test (such as Ishihara plates), further assessment using operationally relevant tests (like lantern or signal light tests) may be permitted. Only those who demonstrate adequate color discrimination for safe flight are certified.

Corrective Lenses and Sunglasses

Corrective spectacles or contact lenses are allowed if they bring vision up to the required standard. Pilots who need corrective lenses must carry a spare pair during flight. Sunglasses should offer 100% UV protection, be optically pure, and avoid distortion. Photochromic (self-darkening) lenses are unsuitable for flight due to slow adaptation to changing light. Polarized lenses can interfere with reading LCD displays and should be avoided.

Light Adaptation and Night Vision

Full adaptation to darkness (maximal rod sensitivity) takes up to 30 minutes, while adaptation to bright light occurs within seconds. Exposure to bright light before night flying can impair night vision. Red cockpit lighting is used to preserve dark adaptation. Night vision is especially vulnerable to hypoxia, and color discrimination is lost in low-light conditions since rods do not detect color.

Depth Perception and Flight Performance

Depth perception relies on binocular vision and visual cues. Accurate color vision aids in interpreting these cues, especially when distinguishing between colored lights or signals. Impaired color vision can reduce the ability to judge distances and interpret visual information, potentially affecting flight safety.