Photosensitive epilepsy
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Photosensitive epilepsy | |
---|---|
Specialty | Neurology |
Frequency | 1 in 4000[1] |
Photosensitive epilepsy (PSE) is a form of
Signs and symptoms
People with PSE experience epileptiform seizures upon exposure to certain visual stimuli. The exact nature of the stimulus or stimuli that triggers the seizures varies from one patient to another, as does the nature and severity of the resulting seizures (ranging from brief
The visual trigger for a seizure is generally cyclic, forming a regular pattern in time or space. Flashing lights (such as strobe lights) or rapidly changing or alternating images (as in clubs, around emergency vehicles, near overhead fans, in action movies or television programs, etc.) are examples of patterns in time that can trigger seizures, and these are the most common triggers. Static spatial patterns such as stripes and squares may trigger seizures as well, even if they do not move. In some cases, the trigger must be both spatially and temporally cyclic, such as a certain moving pattern of bars.
Several characteristics are common in the trigger stimuli of many people with PSE. The patterns are usually high in luminance contrast (bright flashes of light alternating with darkness, or white bars against a black background). Contrasts in colour alone (without changes in luminance) are rarely triggers for PSE. Some patients are more affected by patterns of certain colours than by patterns of other colours. The exact spacing of a pattern in time or space is important and varies from one individual to another: a patient may readily experience seizures when exposed to lights that flash seven times per second, but may be unaffected by lights that flash twice per second or twenty times per second. Stimuli that fill the entire visual field are more likely to cause seizures than those that appear in only a portion of the visual field. Stimuli perceived with both eyes are usually much more likely to cause seizures than stimuli seen with one eye only (which is why covering one eye may allow patients to avoid seizures when presented with visual challenges). Some patients are more sensitive with their eyes closed; others are more sensitive with their eyes open.
Sensitivity is increased by alcohol consumption, sleep deprivation, illness, and other forms of stress.
Television
Television has traditionally been the most common source of seizures in PSE. For people with PSE, it is especially hazardous to view television in a dark room, at close range, or when the television is out of adjustment and is showing a rapidly flickering image (as when the horizontal hold is incorrectly adjusted on analog television sets). Modern digital television sets that cannot be maladjusted in this way and which refresh the image on the screen at very high speed present less of a risk than older, analogue television sets.
Some people with PSE, especially children, may exhibit an uncontrollable fascination with television images that trigger seizures, to such an extent that it may be necessary to physically keep them away from television sets. Some people (particularly those with cognitive impairments, although most people with PSE have no such impairments) self-induce seizures by waving their fingers in front of their eyes in front of bright light or by other means.[2]
UK television broadcasters require all screen content to pass an Automated PSE and QC test. Previously, the
Fluorescent lighting
When functioning correctly, mains-powered fluorescent lighting has a flicker rate sufficiently high (twice the mains frequency, typically 100 Hz or 120 Hz) to reduce the occurrence of problems. However, a faulty
Diagnosis
Diagnosis may be made by noting the correlation between exposure to specific visual stimuli and seizure activity. More precise investigation can be carried out by combining an
Sometimes diagnostic indicators consistent with PSE can be found through provocative testing with IPS, and yet no seizures may ever occur in real-life situations. Many people will show PSE-like abnormalities in brain activity with sufficiently aggressive stimulation, but they never experience seizures and are not considered to have PSE.
Treatment and prognosis
No cure is available for PSE, although the sensitivity of some people may diminish over time. Medical treatment is available to reduce sensitivity, with
Epidemiology
PSE affects approximately one in 4,000 people, or 5% of individuals with epilepsy.[1] It is more common in women and people who are younger.[1]
Society and culture
Law
A law requiring PSE warnings be displayed on packages and stores was proposed by the State of New York.[9][failed verification – see discussion]
Games
The first case of epileptiform seizures related to a video game was reported in 1981.[10] Since then, "many cases of seizures triggered by video games were reported, not only in photosensitive, but also in nonphotosensitive children and adolescents with epilepsy... Specific preventive measures concerning the physical characteristics of images included in commercially available video games (flash rate, choice of colours, patterns, and contrast) can lead in the future to a clear decrease of this problem."[10] Risks can be reduced through measures such as keeping a safe distance away from the screen (at least 2 meters).[10]
While computer displays in general present very little risk of producing seizures in PSE patients (much less risk than that presented by television sets), video games with rapidly changing images or highly regular patterns can produce seizures, and video games have increased in importance as triggers as they have become more common. Some people with no prior history of PSE may first experience a seizure while playing a video game. Often the sensitivity is very specific, e.g., it may be a specific scene in a specific game that causes seizures, and not any other scenes. Despite this, there are questions on the dangers of this, and calls for testing all video games for causing PSE.[11]
Web design
As with video games, rapidly changing images or highly regular patterns such as flashing banner ads or irregular fonts can trigger seizures in people with photosensitive epilepsy. Two sets of guidelines exist to help web designers produce content that is safe for people with photosensitive epilepsy:
- The World Wide Web Consortium - Web Content Accessibility Guidelines (WCAG) Version 2.0, produced in 2008, specifies that content should not flash more than three times in any one-second period.[12] However, it does allow flashing above this rate if it is below the "general and red flashing thresholds", which means if the effect is small or low-contrast enough it is acceptable.[13]
- In the
Public incidents
Photosensitive epilepsy was again brought to public attention in December 1997 when the
In March 1997, the 25th episode of an anime series called YAT Anshin! Uchū Ryokō caused a similar incident, when a reported four children were taken to hospitals by ambulances after viewing a scene with red and white flashing colours.[17]
In March 2008, the
An animated segment of a film promoting the
In December 2016,
The 2018 Pixar film Incredibles 2 contains scenes with flashing lights starting about an hour into the film, in which a villain called the Screenslaver hypnotizes other characters. After concerns over possible triggering of seizures due to this scene, theatres posted warnings for audiences with this condition.[23]
See also
References
- ^ PMID 28532712.
- S2CID 19739107.
- ^ "How is TV made safe for people with epilepsy?". 7 June 2007. Retrieved 26 January 2020.
- ^ "London 2012 logo footage withdrawn amid epilepsy fears". Reuters. 6 June 2007. Retrieved 26 January 2020.
- ^ "BATON®, Enterprise-class Automated File-based QC".
- ^ "Vidchecker Widely Adopted in UK, New Version Set For BVE". tvtechnology.com. 14 January 2015.
- ^ "Section two: Harm and offence". Ofcom. 18 July 2017. Retrieved 26 January 2020.
- ^ "New regulation for photosensitive epilepsy testing devices | Jigsaw24". Jigsaw24.com. Retrieved 26 January 2020.
- ^ "Bills". Assembly.state.ny.us. Retrieved 21 November 2013.
- ^ S2CID 2044136.
- ^ "Video games campaign | Epilepsy Action". Epilepsy.org.uk. 18 October 2012. Retrieved 21 November 2013.
- W3C. 5 June 2018. Retrieved 9 June 2018.
- W3C. 5 June 2018. Retrieved 9 June 2018.
- ^ "Section 508 Standards - Section508.gov".
- (PDF) from the original on 30 October 2018.
- ^ "Japanese cartoon triggers seizures in hundreds of children". CNN. Reuters. 17 December 1997. Archived from the original on 26 August 2019. Retrieved 29 September 2007.
- ^ "An Interim Report from the "Study Group on Broadcasting and Audio-Visual Sensory Perception"". Ministry of Posts and Telecommunications. April 1998. Archived from the original on 23 October 2008. Retrieved 2 November 2008.
- ^ a b Ramadge, Andrew (1 April 2008). "Anonymous attack targets epilepsy sufferers". news.com.au. Archived from the original on 26 December 2009. Retrieved 8 December 2013.
- ^ a b Poulsen, Kevin (28 March 2008). "Hackers Assault Epilepsy Patients via Computer". Wired. Archived from the original on 26 December 2019. Retrieved 8 December 2013.
- ^ "Epilepsy fears over 2012 footage". BBC News. 5 June 2007. Archived from the original on 23 March 2019. Retrieved 5 June 2007.
- ^ Hawkins, Derek (21 December 2016). "Newsweek Trump critic says he had epileptic seizure after Twitter troll purposely sent him flashing image". The Washington Post. Archived from the original on 26 December 2019. Retrieved 26 December 2019.
- ^ "US man held for sending flashing tweet to epileptic writer". BBC News. 18 March 2017. Archived from the original on 2 November 2019. Retrieved 18 March 2017.
- ^ Svachula, Amanda (18 June 2018). "'Incredibles 2' Moviegoers Warned About Possible Seizures". The New York Times. Archived from the original on 26 December 2019. Retrieved 3 July 2018.
- ^ Ruppert, Liana. "Cyberpunk 2077 Epileptic PSA", Game Informer, 7 December 2020.
- ^ Lyles, Taylor (8 December 2020). "Cyberpunk 2077 to add new epilepsy warning as devs work on a permanent fix". The Verge.
- ^ "New Cyberpunk 2077 Update Addresses Major Epilepsy Issue". Game Informer.
Further reading
- Bureau M, Hirsch E, Vigevano F (2004). "Epilepsy and videogames". Epilepsia. 45 Suppl 1: 24–6. S2CID 2044136..
- Harding, Graham F.A.; Jeavons, Peter M. (1994). Photosensitive Epilepsy. Clinics in Developmental Medicine (New ed.). London: Mac Keith Press. LCCN 2008531085.
External links
- HardingFPA Broadcast Flash and Pattern Analyser
- Photosensitive+Epilepsy at the U.S. National Library of Medicine Medical Subject Headings (MeSH)