The patterns are usually high in luminance contrast (bright flashes of light alternating with darkness, or white bars against a black background).
An automated file-QC system like BATON implements algorithms to detect PSE levels based on the restrictions described in ITU-R BT.1702, Ofcom, and NAB-J guidelines.
[medical citation needed] Newer high-efficiency compact fluorescent lamps (CFL) with electronic ballast circuits operate at much higher frequencies (10–20 kHz) not normally perceivable by the human eye, though defective lights can still cause problems.
[medical citation needed] Diagnosis may be made by noting the correlation between exposure to specific visual stimuli and seizure activity.
The testing physician adjusts the IPS device and looks for characteristic anomalies in the EEG, such as photoparoxysmal response (PPR), that are consistent with PSE and/or may herald the onset of seizure activity.
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.
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] 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.
[11] 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: Photosensitive epilepsy was again brought to public attention in December 1997 when the Pokémon episode "Dennō Senshi Porygon" ("Cyber Soldier Porygon") was broadcast in Japan, showing a sequence of flickering images that triggered seizures simultaneously in hundreds of susceptible viewers (although 12,000 children reported symptoms which may be attributable to mass hysteria).
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.
Later attacks redirected web browsers to a page with "a more complex image designed to trigger seizures in both photosensitive and pattern-sensitive epileptics.
[20] In December 2016, Newsweek journalist Kurt Eichenwald, who has epilepsy, reportedly had a seizure after an internet troll intentionally sent him a flashing GIF via Twitter.
[23] Cyberpunk 2077, a video game released in December 2020, contains a "braindance" sequence with red and white flashing lights which reportedly resembles the patterns produced by medical devices used to intentionally trigger seizures.
[24] After criticism from epilepsy advocacy groups that the game's disclaimers were insufficient, CD Projekt Red announced work on a fix[25] and later patched the effect to be less likely seizure-inducing.