Flicker or pattern sensitivity is a student's physiological response to a rapid switching back and forth of visual stimuli from high to low brightness or shifting patterns.
Students with flicker or pattern sensitivity have a physiological reaction to repetitive patterns, flickering video, or stroboscopic lights. Depending on the specific disability, the student's reaction might take the form of a seizure, pain, or visual overload. A flicker rate of 15 - 20 Hz is considered to be the most likely to trigger a physiological response. Flicker at or above 60 Hz are relatively safe as are very low rates, although seizures have been triggered at as few as 3 Hz.

• Diagnosis of photosensitive epilepsy
• Diagnostic information referring to sensitivity to pattern or flicker.

• When you see flashing lights or fast moving video do you become queasy or have a seizure?
• Do complicated patterns such as optical illusions make you feel like you are motion sick?
• Do quickly moving objects like fans or shadows from trees make you feel disoriented or off-balance?
• What accommodations or strategies have been effective in the past?

• American Epilepsy Society
  http://www.aesnet.org/
• Epilepsy Foundation of America
  http://www.epilepsyfoundation.org/
• WCAG 2.0 Flash Guidelines
  http://www.w3.org/TR/WCAG20/#general-thresholddef
• Canadian Epilepsy Alliance
  http://www.epilepsymatters.com/english/faqphotosensitive.html
• TRACE Photosensitive Epilepsy Analysis Tool
  http://trace.wisc.edu/peat/