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After the eyes have adapted to the dark, the entire process is reversed when entering a lighted room. The eyes are fi rst dazzled by the brightness, but become completely adjusted in a few seconds, thereby losing their adaptation to the dark. Now, if the dark room is reentered, the eyes again go through the long process of adapting to the darkness. 

Before and during night flight, the pilot must consider the adaptation process of the eyes. First, the eyes should be allowed to adapt to the low level of light. Then, the pilot should avoid exposing them to any bright white light that would cause temporary blindness and possibly result in serious consequences. 

Temporary blindness, caused by an unusually bright light, may result in illusions or afterimages until the eyes recover 

from the brightness. The brain creates these illusions reported by the eyes. This results in misjudging or incorrectly identifying objects, such as mistaking slanted clouds for the horizon or a populated area for a landing field. Vertigo is experienced as a feeling of dizziness and imbalance that can create or increase illusions. The illusions seem very real and pilots at every level of experience and skill can be affected. Recognizing that the brain and eyes can play tricks in this manner is the best protection for flying at night. 

Good eyesight depends upon physical condition. Fatigue, colds, vitamin deficiency, alcohol, stimulants, smoking, or medication can seriously impair vision. Keeping these facts in mind and taking appropriate precautions should help safeguard night vision. 

