Flicker vertigo, sometimes called the Bucha effect, is "an imbalance in brain-cell activity caused by exposure to low-frequency flickering (or flashing) of a relatively bright light." It is a

disorientation Orientation is a function of the mind involving awareness of three dimensions: time, Location (geography), place and person. Problems with orientation lead to ''dis''orientation, and can be due to various conditions, from delirium to Substance int ...

vertigo Vertigo is a condition where a person has the sensation of movement or of surrounding objects moving when they are not. Often it feels like a spinning or swaying movement. This may be associated with nausea, vomiting, sweating, or difficulties w ...

-, and

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...

-inducing effect of a

strobe light A strobe light or stroboscopic lamp, commonly called a strobe, is a device used to produce regular flashes of light. It is one of a number of devices that can be used as a stroboscope. The word originated from the Ancient Greek ('), meaning ...

flashing at 1 Hz to 20 Hz, approximately the frequency of human

brainwaves Neural oscillations, or brainwaves, are rhythmic or repetitive patterns of neural activity in the central nervous system. Neural tissue can generate oscillatory activity in many ways, driven either by mechanisms within individual neurons or by ...

. The effects are similar to seizures caused by

epilepsy Epilepsy is a group of non-communicable neurological disorders characterized by recurrent epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal electrical ...

(in particular

photosensitive epilepsy Photosensitive epilepsy (PSE) is a form of epilepsy in which seizures are triggered by visual stimuli that form patterns in time or space, such as flashing lights; bold, regular patterns; or regular moving patterns. PSE affects approximately o ...

), but are not restricted to people with histories of epilepsy. This phenomenon has been observed during

helicopter A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...

flight; a Dr. Bucha identified the phenomenon in the 1950s when called upon to investigate a series of similar and unexplained helicopter crashes. Flicker vertigo in a helicopter occurs when the pilot or front passenger looks up through the blades of the main

rotor Rotor may refer to: Science and technology Engineering *Rotor (electric), the non-stationary part of an alternator or electric motor, operating with a stationary element so called the stator * Helicopter rotor, the rotary wing(s) of a rotorcraft ...

as it turns in the

sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

causing the

light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...

strobe A strobe light or stroboscopic lamp, commonly called a strobe, is a device used to produce regular flashes of light. It is one of a number of devices that can be used as a stroboscope. The word originated from the Ancient Greek ('), meaning ...

. The

effect can cause persons who are vulnerable to flicker vertigo to experience symptoms such as: * Become disoriented and/or nauseated * Blink rapidly * Experience rapid eye movements behind closed eyelids * Lose control of fine motor functions * Experience muscle rigidity These effects are typically very minor and will most often subside within seconds once exposure to the strobe effect has ceased, though residual nausea and minor disorientation may be felt for several minutes. In extremely rare cases, severe reactions can happen including: * Total persistent loss of bodily functions * Loss of muscle/motor response * Loss of control of aircraft or other moving vehicles *

Seizure An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with los ...

This situation can occur whenever flickering light conditions exist. Examples of this include: * Using electronics on low-light conditions for extended periods * Sunlight flickering through a tree-lined street * Sunlight reflecting off of water, especially off of rippling waves * Fixed wing flight * Looking at or through a slowly spinning propeller According to The US Naval Flight Surgeons Manual, flicker vertigo is a rare occurrence. Flicker vertigo has been considered as a principle for various forms of

non-lethal weapon Non-lethal weapons, also called nonlethal weapons, less-lethal weapons, less-than-lethal weapons, non-deadly weapons, compliance weapons, or pain-inducing weapons are weapons intended to be less likely to kill a living target than conventional ...

s. A related crowd-control device was invented by Charles Bovill, which "employed a combination of ultra-sonic waves and strobe lights to induce acute discomfort, sickness, disorientation and sometimes epilepsy."

References

{{Reflist

External links

Flight Safety Foundation

Flicker illness: an underrecognized but preventable complication of helicopter transport.

filed in 2005 — a patent for a device based on this phenomenon.

''Wired'' Danger Room blog, February 20, 2007 — a description of a weapon based on a similar phenomenon. Neurological disorders

See also

References

External links