People with<unk>  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 absence seizures to full tonic–clonic seizures). Many<unk>  patients experience an "aura" or feel odd sensations before the seizure occurs, and this can serve as a warning to a patient to move away from the trigger stimulus. The visual trigger for a seizure is generally cyclic, forming a regular pattern in time or space. Flashing 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, and Mazes 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<unk> . 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<unk> . 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<unk> . For people with<unk> , 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, analog television sets. Some people with<unk> , 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<unk>  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. UK television broadcasters require all screen content to pass an Automated<unk>  and QC test. Previously, the Harding FPA Test was used to assess content, however this has been replaced by software such as BATON or Vidchecker. Ofcom regularly updates their definition of a flashing sequence. This is an objective standard of assessment of potential to trigger seizures in the susceptible population. This test is not currently required internationally. An automated file-QC system like BATON implements algorithms to detect<unk>  levels based on the restrictions described in ITU-R BT.1702, Ofcom, and NAB-J guidelines. The recent versions of BATON support Ofcom, NAB-J, ITU-T BT. 1702 (2005 and ITU-R BT. 1702 (2018), there are plans to support ITU BT.1702-2 (10/2019) as well in the upcoming release. 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 fluorescent lamp can flicker at a much lower rate and trigger seizures. 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.
Photosensitive epilepsy
Vertiginous epilepsy
Northern epilepsy syndrome
Musicogenic epilepsy
Generalized epilepsy
Temporal lobe epilepsy
Nocturnal epilepsy
Occipital epilepsy