Redout is a visual phenomenon caused by negative G-forces, resulting in a rush of blood to the head and a reddish, blurry vision. It can cause damage to the eyes and brain, and pilots must take precautions to avoid it. Other visual distortions can also occur during flight, and pilots should report any unusual vision to receive medical evaluation.
Redout is a visual phenomenon associated with negative G-forces in which a person’s field of vision turns red due to a sudden rush of blood to the head. A classic example of a situation where this can occur is in aerobatic flight where a pilot makes a sudden steep dive, subjecting his body to negative G-forces. This can be very dangerous and pilots must take care to protect their bodies from the stress of acceleration. Positive G-forces, such as when people suddenly climb and accelerate, can cause the opposite problem, a flow of blood away from the head, leading to graying of the visual field, confusion and other problems.
Physiologically, during a redout the blood vessels inside the eyes expand, creating blurry, reddish vision. If they expand enough, they can break. The patient may develop damage to the retina, and the blood flowing freely within the head may also lead to hemorrhagic stroke, in which brain cells begin to die due to pressure buildups within the skull. During a redout, the patient may lose consciousness or become confused and sluggish as tissues within the brain begin to suffer damage.
Pilots in training for situations where they will encounter G-forces go through a series of rigorous tests to ensure they can handle the high stress associated with things like aerobatic flying, piloting military aircraft, and operating space ships and shuttles. This includes simulated ground conditions where pilots are placed in a very high acceleration stress environment to see how their bodies respond. Safety equipment helps prevent some injuries, and patients should have regular health exams to ensure they are still fit for service in environments where high G-forces will be present.
If a pilot begins to notice redout during flight, it may be necessary to slow down and adjust the flight plan to avoid eye and brain damage. Pilots typically maintain constant communication with ground control, as well as other pilots in the air, and can alert people that there is a problem and they may need medical assistance on the ground. An ophthalmologist can check the pilot’s eyes for signs of injury, and a neurological evaluation may also be needed to check for any brain injuries.
In addition to redout, other distortions of the visual field can occur during flight. Vision can turn white or gray when blood flows away from the head and towards the feet, a warning that the pilot’s brain is not getting enough blood. Tunnel vision can also occur. Pilots who notice anything unusual with their vision should report it so they can receive a medical evaluation.
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