ISO 9241-391:2016 provides requirements and recommendations for reducing photosensitive seizures (PSS), while viewing images on electronic displays.The requirements and recommendations in this part of ISO 9241 are designed to be applied to image contents. By image contents, reference is made to the images independent of the device or environment in which they are displayed.The requirements and recommendations in this part of ISO 9241 are for the protection of the vulnerable individuals in the viewing population who are photosensitive and who are therefore liable to seizures triggered by flashing lights and regular patterns, including certain repetitive images.NOTE 1 ITU considers the image safety issues in relation to broadcasting. Some of these are described in ITU-R BT.1702.[2]NOTE 2 There are some related recommendations in ISO/IEC 40500:2012, W3C Web Content Accessibility Guidelines (WCAG) 2.0, for web contents accessibility.NOTE 3 Photosensitive seizures and photosensitive epilepsy, that is, chronic conditions characterized by those repeated seizures are medical conditions. Clinical aspects of photosensitivity appear in Annex C. Visually induced seizures are equivalent to PSS.