flicker vertigo

{{Short description|Vertigo caused by strobe light}}

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."[http://www.flightsafety.org/members/serveme.cfm?path=hf/hf_mar-apr04.pdf (online article requires logon)] {{Webarchive|url=https://web.archive.org/web/20070928175829/http://www.flightsafety.org/members/serveme.cfm?path=hf%2Fhf_mar-apr04.pdf |date=2007-09-28 }} Clarence E Rash: Awareness of Causes and Symptoms of Flicker Vertigo Can Limit Ill Effects: Human Factors and Aviation Medicine: Vol 51: Number 2: Mar-Apr 2004: Flight Safety Foundation It is a disorientation-, vertigo-, and nausea-inducing effect of a strobe light flashing at 1 Hz to 20 Hz, approximately the frequency of human brainwaves.{{Citation | last = Bunker| first = Robert J.| title=Nonlethal Weapons: Terms and References | date = July 1997 | page = 17 | publisher = DIANE| isbn = 9781428991934 | url = https://books.google.com/books?id=aoZYYz1ZieYC&dq=%22Bucha+effect%22&pg=PA17 }}{{Citation | last = Lyell | title = Non-lethal Weapons: Draft General Report | date = September 1997 | page = 3 | url = http://natopa.ibicenter.net/archivedpub/comrep/1997/ap238ste.pdf | access-date = 2012-04-16 | archive-date = 2012-02-22 | archive-url = https://web.archive.org/web/20120222165625/http://natopa.ibicenter.net/archivedpub/comrep/1997/ap238ste.pdf | url-status = dead }} 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.{{citation needed|date=January 2022}} Flicker vertigo 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 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

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 water, especially off of rippling waves
• Fixed wing flight
• Looking at or through a slowly spinning propeller

{{Citation | last = Ronson | first = Jon | title= The men who stare at goats | date = 2005 | page = 147 | publisher = Simon and Schuster | isbn = 9780743241922 | url = https://books.google.com/books?id=2htuO07UAUoC&dq=Bucha+effect&pg=PA147}}

According to The US Naval Flight Surgeons Manual, flicker vertigo is a rare occurrence.[http://www.narcap.org/PerceptualDisorders.htm National Aviation Reporting Center on Anomalous Phenomena] {{Webarchive|url=https://web.archive.org/web/20061210215634/http://www.narcap.org/PerceptualDisorders.htm |date=2006-12-10 }} United States Naval Flight Surgeon's Manual: Third Edition 1991: Chapter 9: Ophthalmology: Perceptual Disorders; Naval Aerospace Medical Institute

Flicker vertigo has been considered as a principle for various forms of non-lethal weapons.{{Citation | last = Bertomen| first = Lindsey| title=You Strobe, I Strobe, We All Strobe Together | journal = Law Enforcement Technology | date = May 2007 | url = http://www.officer.com/print/Law-Enforcement-Technology/You-Strobe--%C2%ADI-Strobe--We-All-Strobe-Together/1$36370 }}{{cite journal|last=Patel|first=Prachi|title=The Incapacitating Flashlight; An LED flashlight makes culprits vomit.|journal=MIT Technology Review|date=2007-08-06|url=http://www.technologyreview.com/news/408360/the-incapacitating-flashlight/|accessdate=17 July 2013}} 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."{{Citation | title = Charles Bovill Obituary | date = November 2001 |publisher = The Daily Telegraph |url = https://www.telegraph.co.uk/news/obituaries/1329575/Charles-Bovill.html}}