Photosensitive epilepsy

A form of epilepsy in which seizures are triggered by visual stimuli such as flashing lights, strobing effects, rapid colour transitions, or high-contrast repeating patterns. It affects approximately 3 to 5 percent of people with epilepsy and is more common in children and adolescents. Flashing between 5 and 30 times per second poses the greatest risk, though individual thresholds vary and can fluctuate with sleep, stress, and medication. In web accessibility, photosensitive epilepsy is directly addressed by WCAG Success Criterion 2.3.1, which requires that content must not flash more than three times per second unless the flash is below the general flash and red flash thresholds. Tools such as the Photosensitive Epilepsy Analysis Tool (PEAT) and the Harding Flash and Pattern Analyzer can test content for compliance.