What physical condition can lead to impaired night vision in pilots?

A vitamin A deficiency can lead to impaired night vision in pilots due to its critical role in the formation of visual pigments necessary for low-light vision. Vitamin A is essential for the production of rhodopsin, a pigment found in the rod cells of the retina that enables vision in dim light. Without adequate vitamin A, the body cannot produce enough rhodopsin, resulting in difficulty seeing in low-light conditions, commonly known as night blindness.

The other deficiencies listed do not directly impact night vision in the same way. For example, iron deficiency primarily affects oxygen transport in the blood and may lead to fatigue, but it does not have a direct effect on the photoreceptor cells responsible for night vision. Likewise, calcium and folate deficiencies influence other bodily functions, like bone health and DNA synthesis, respectively, but they are not linked to the visual processes needed for seeing well in the dark. Therefore, maintaining adequate levels of vitamin A is essential for pilots to ensure optimal night vision and overall visual performance.