Photic- and Pattern-induced Seizures: Expert Consensus of the Epilepsy Foundation of America Working Group


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Summary: Purpose: In August, 2004, the Epilepsy Foundation of America convened a workshop to begin to develop an expert consensus on photosensitive seizures.

Methods: Literature and data were reviewed, and consensus was derived from discussion.

Results: A flash is a potential hazard if it has luminance ≥20 cd/m2, occurs at a frequency of ≥3 Hz, and occupies a solid visual angle of ≥0.006 steradians (∼10% of the central visual field or 25% of screen area at typical viewing distances). A transition to or from saturated red also is considered a risk. A pattern with the potential for provoking seizures contains clearly discernible stripes, numbering more than five light–dark pairs of stripes in any orientation. When the light–dark stripes of any pattern collectively subtend at the eye from the minimal-expected viewing distance a solid angle of >0.006 steradians, the luminance of the lightest stripe is >50 cd/m2, and the pattern is presented for ≥0.5 s, then the pattern should display no more than five light–dark pairs of stripes, if the stripes change direction, oscillate, flash, or reverse in contrast; if the pattern is unchanging or smoothly drifting in one direction, no more than eight stripes. These principles are easier to apply in the case of fixed media, for example, a prerecorded TV show, which can be analyzed frame-by-frame, as compared with interactive media.

Conclusions: A consensus view of stimuli likely to provoke visually evoked seizures can be developed.