Characterizing the Flashing Television Images that Precipitate Seizures

“…1, panel 2, it is possible to estimate the proportion of patients affected by patterns that occupy different areas of the screen, bearing in mind the simplifying assumptions outlined earlier. After previous work (6), we assume that 100% of patients is affected by patterns that occupy all of the screen of a 20‐inch television (diametric measurement). The proportion affected by patterns that occupy one half, one fourth, one eighth, and one tenth of the screen area can be calculated on the basis of Fig.…”

Section: Effects Of Spatial Frequencymentioning

confidence: 99%

“…These data were obtained by using a stationary pattern (Ref. 2, p. 20) and differ from those used previously to estimate the effects of flicker (6).…”

Section: Effects Of Spatial Frequencymentioning

confidence: 99%

Characterizing the Patterned Images That Precipitate Seizures and Optimizing Guidelines To Prevent Them

Wilkins

Emmett²,

Harding

2005

Epilepsia

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Summary:The use of guidelines to prevent the broadcast of epileptogenic television program content has reduced the incidence of seizures in Britain and Japan. Epileptogenic content includes both flicker and patterns. The guidelines for flicker were developed on the basis of a model that related stimulus parameters to the proportion of patients affected. We here extend the model to pattern stimuli. A set of rules is advocated that keeps the level of risk to a consistent minimum and simplifies compliance. We propose that striped patterns that last >0.5 s, occupy more than one fourth the area of the screen, and have bright stripes >50 cd/m 2 in luminance be restricted as regards the number of cycles admissible. The guidelines are estimated to protect at least two thirds of susceptible patients.

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“…A Monarch Instrument Nova-Strobe PBL strobe light was used to simulate temporal sampling at different frame (flash) rates. To reduce the risk of photosensitive epilepsy, the lowest flash rate of the strobe was set to 60 Hz [25]. To ensure that impulsive sampling was simulated, the duty cycle of the strobe (akin to the shutter angle of a video camera) was set such that the distance traveled by the line within a flash was always smaller than the spatial acuity of the human eye, which we assumed to be 1 arc min as a worse case scenario [27].…”

Section: Experimental Setup and Methodologymentioning

confidence: 99%