Visual displays and indicators shall minimize visual flicker that might induce seizures in people with photosensitive epilepsy.
1. Individuals with photo-sensitive epilepsy can have a
seizure triggered by displays which flicker or flash, particularly if the flash
has a high intensity and within certain frequency ranges.
2. Strategies to address this requirement involve reducing
or eliminating screen flicker or image flashing to the extent possible. In
particular, the rates of 2 Hz or lower or
70 Hz or higher are recommended. This recommendation reflects current
research data on people with photosensitive epilepsy which indicates that the
peak sensitivity for these individuals is 20 Hz and that the sensitivity then
drops off in both directions.
3. The chance of triggering seizures can also be reduced by avoiding very bright flashes which occupy a large part of the visual field (particularly in the center of the visual field) in order to minimize the impact on the visual cortex.
During our research we found no products that violated this Guideline, largely because few products have flashing displays of appreciable brightness. Note that some flashing telephone alerting devices may indeed violate it.