<unk> , sometimes called the Bucha effect, is "an imbalance in brain-cell activity caused by exposure to low-frequency<unk> ing (or flashing) of a relatively bright light." It is a disorientation-,<unk> -, and nausea-inducing effect of a strobe light flashing at 1 Hz to 20 Hz, approximately the frequency of human brainwaves. The effects are similar to seizures caused by epilepsy (in particular photosensitive epilepsy), but are not restricted to people with histories of epilepsy. This phenomenon has been observed during helicopter flight; a Dr. Bucha identified the phenomenon in the 1950s when called upon to investigate a series of similar and unexplained helicopter crashes.<unk>  in a helicopter occurs when the pilot or front passenger looks up through the blades of the main rotor as it turns in the sun causing the light to strobe. The strobe light effect can cause persons who are vulnerable to<unk>  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 This situation can occur whenever<unk> ing light conditions exist. Examples of this include: * Using electronics on low-light conditions for extended periods * Sunlight<unk> ing 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,<unk>  is a rare occurrence.<unk>  has been considered as a principle for various forms of non-lethal weapons. 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."
Flicker vertigo
Alternobaric vertigo
Positional alcohol nystagmus
Migraine-associated vertigo
Ictal headache
Trigeminal trophic syndrome
Benign paroxysmal positional vertigo
Amaurotic nystagmus