Improving product accessibility for users with epilepsy

Practical design strategies for the safety and inclusion of people with epilepsy

Illustration by Louis Wes

But what if the ending is different? What if, aside from feeling disoriented, that GIF risks your life? What if, after opening the web page, you lose consciousness, time passes, and you wake up on the floor with EMTs and your loved ones around you. They’re scared and feel powerless. You feel confused, tired, sore, hurt, ashamed... and lucky.

For someone with photosensitive epilepsy, this experience isn't hypothetical, it's a daily probability. As someone who has experienced these challenges firsthand, I know how much harm inaccessible designs can cause.

I've had epilepsy for the past 17 years. For 14 of those years, I've also designed digital products. I've dedicated the remainder of my career to ensuring that the digital products and media I work on follow accessibility guidelines, while also being functional and enjoyable. There are practical strategies designers and engineers can employ to design for the safety and inclusion of people with epilepsy.

The stakes are high

According to the World Health Organization, around 50 million people worldwide have epilepsy, making it one of the most common neurological diseases globally. It affects people of all ages. It involves recurrent seizures, which are brief episodes of involuntary movement that may include a part of the body (partial) or the entire body (generalized) and, sometimes, loss of consciousness. Commonly reported triggers include:

• Lack of sleep
• Illness, both with and without fever
• Flashing bright lights or patterns
• Stress, both good and bad
• Hormonal changes
• Poor diet, dehydration, low blood sugar, vitamin and mineral deficiencies
• Use of certain medications and missed medications

During a seizure, it’s impossible to know what cognitive abilities someone might lose, or whether they’ll survive. Seizures lasting over five minutes have a mortality rate of 7% (39% in severe cases). While not all users face these risks, neurological impairments like epilepsy can make some media and interfaces dangerous. Flashing, flickering, or high-contrast visuals can trigger seizures, nausea, or dizziness. Even well-meaning designs can inadvertently harm users. Design decisions that can exclude or contribute to harm often arise from:

• Lack of education: Many designers and engineers are unaware of the risks posed by flashing or strobing visuals.
• Prioritization of aesthetics: Eye-catching designs and animations often take precedence over usability and safety.
• Misaligned metrics: Business goals like engagement or uniqueness can lead to decisions that compromise accessibility.

Design practices for preventing harm in people with epilepsy

Ensuring that web content is safe for all users, including those with photosensitive epilepsy, is both a moral obligation and a legal requirement. The Mozilla Developer Network (MDN) offers invaluable guidance that emphasizes the importance of adhering to established accessibility standards, but minimizing harm begins with understanding the risks and following accessibility principles. There are actionable strategies that focus on preventing harm while improving usability for everyone.

Measure visual stimuli using ethical tools

It's crucial to measure and control visual stimuli to safeguard users from content that could trigger seizures. MDN highlights the significance of monitoring flashing content to ensure it doesn't exceed safe thresholds. Specifically, content should only flash up to three times per second unless the flashes are below general flash and red flash thresholds. It aligns with the Web Content Accessibility Guidelines (WCAG) 2.2, which provides comprehensive criteria for web accessibility.

Effectively measuring and controlling visual stimuli, by incorporating findings from accessibility testing into the design and development process, is crucial to safeguarding users from content that could trigger seizures. But user testing for accessibility can be challenging, especially for impairments like photosensitivity. MDN emphasizes tools and tests to ensure that web content adheres to safe standards for photosensitive individuals. Two ethical tools mentioned by MDN can help assess the risks of visual media without endangering users:

• The Photosensitive Epilepsy Analysis Tool (PEAT) helps developers analyze web content for potential seizure triggers. It identifies problematic visual elements, such as flashing patterns or excessive brightness, and provides actionable insights to mitigate these risks. Using PEAT early in the design and testing phases ensures safer content for users with photosensitive conditions. Note that PEAT’s use is restricted to commercial broadcasting, so alternatives like the Harding Test should be used when necessary.
• The Harding Test is a widely recognized method for evaluating the safety of visual stimuli. The test applies algorithms to determine whether flashing content or patterns fall within safe thresholds. Incorporating this test into the quality assurance process ensures that content stays below the general flash and red flash thresholds outlined in the WCAG 2.2.

Ensure compliance with Web Content Accessibility Guidelines 2.2

Compliance with WCAG 2.2 is essential for creating accessible web content. Guideline 2.3 specifically addresses seizures and physical reactions and advises against designing content in ways known to cause such issues. Flashing or strobing visuals are particularly hazardous for users with photosensitive epilepsy. Content that flashes at frequencies between 3 Hz and 30 Hz is most likely to trigger seizures.

What you can do: Avoid flashing, flickering, and blinking visuals, and replace hazardous media with static alternatives, or videos with play/pause controls instead of flashing GIFs. Adhering to these guidelines not only protects users but also ensures legal compliance.

Design for predictability and control, and use media queries to empower users

Users with neurological conditions may struggle with interfaces that feel chaotic or out of their control. Be mindful of high-contrast patterns and bright, rapidly changing colors, as they can be triggers, but also respect people’s autonomy and enhance their safety by giving them control over their interactions and their experience.

• Provide warnings: When flashing content is unavoidable offer clear warnings to users before they encounter it. If potentially harmful visuals are unavoidable, include clear warnings and allow users to opt in before viewing.
• Minimize animations. Respect user preferences by disabling non-essential animations when “prefers-reduced-motion” is enabled.
• Allow pause or stop for animations. Provide mechanisms for users to pause or stop any moving, blinking, or auto-updating content.
• Offer customization options. Enable users to adjust or turn off animations and flashing content according to their preferences.
• Provide playback controls. For videos or animations, include start, pause, and speed settings.
• Create straightforward navigation. Design intuitive navigation structures that help users avoid unexpected content that might be harmful.
• Enhance contrast safely. Use “prefers-contrast” to adjust text and background contrast levels without creating excessive visual strain.

Simplify interfaces for cognitive accessibility

Designing for cognitive impairments is essential for creating user experiences that accommodate individuals with epilepsy who may have developed them following seizures. These impairments can significantly impact daily functioning, making thoughtful design crucial for accessibility and usability. Individuals with epilepsy often face cognitive challenges, including:

• Memory impairments: Difficulties in retaining new information and recalling past events are common. (Source: MDPI)
• Attention deficits: Maintaining focus can hinder task completion and information processing. (Source: MECP)
• Executive dysfunction: Problems with planning, decision-making, and problem-solving can affect daily activities. (Source: Frontiers)

Cognitive impairments, including short-term memory challenges, require designs that prioritize clarity and focus.

These cognitive issues can stem from epilepsy itself, seizure frequency, and side effects of antiepileptic medications (Source: MDPI). To address these challenges, consider the following design strategies mentioned in detail in Accessibility and W3C:

• Simplify navigation. Use clear, consistent layouts with intuitive navigation to reduce cognitive load.
• Offer clear instructions. Use straightforward, concise instructions to aid comprehension and task execution.
• Use plain language. Employ simple language to enhance understanding and reduce confusion.
• Incorporate visual aids. Utilize icons and images to support text to aid memory and comprehension.
• Allow customization. Enable users to adjust text size, contrast, and other settings to suit their preferences.
• Provide feedback. Offer immediate, clear feedback for user actions to confirm successful completion or to highlight errors.
• Limit distractions. Minimize unnecessary animations and auto-playing media that can divert attention.
• Ensure consistency. Maintain uniformity in design elements to create a predictable environment, aiding user orientation.
• Avoid placeholder labels. Use labels outside input fields to ensure users can always reference instructions.
• Chunk information. Divide complex information into smaller, digestible steps with progress indicators.
• Reduce visual clutter. Design clean interfaces with ample spacing and a logical hierarchy.
• Reduce cognitive load. Simplify interfaces by breaking tasks into smaller, clear steps. Persistent toast racks can ensure important messages aren’t lost.

Educate teams about accessibility risks

Preventing harm requires awareness among all stakeholders. Many designers and engineers simply don’t know the impact their decisions can have on users with impairments. What you can do:

• Run accessibility workshops. Teach your team about WCAG standards and the risks of flashing visuals.
• Share real-world stories. Highlight how inaccessible designs have affected users, including examples of weaponized media.
• Document best practices. Create internal libraries or guidelines that outline accessibility strategies.

Implementing these practices fosters an inclusive digital environment, enhancing usability for individuals with cognitive impairments. Integrating them into product development is not just about compliance, it's about fostering an inclusive and safe digital space for everyone. MDN offers comprehensive insights into this critical aspect of web accessibility and by adhering to these guidelines, and the WCAG 2.2 standards, we can create web experiences that are both engaging and safe for all users.

A call to action and a framework for safer, inclusive design

As I write my story today, somebody could tell it any other day—because it’s a reality familiar to many. Regardless of age or neurological condition, interruptions, context switching, and moments of disorientation are part of life. Forgetting what we’re working on isn't a human error; it's an inevitable outcome of navigating an increasingly complex world. But using software interfaces and consuming media should be intuitive, safe, and require minimal mental effort. Unfortunately, many digital experiences still fall short.

Designers and engineers have the power to create a digital world that works for everyone. Together, we can make technology safer, more inclusive, and empowering for all users. Designing for accessibility isn’t limited to meeting guidelines, it includes creating experiences that empower all users, and there’s a simple framework to guide efforts:

1. Start with empathy. Understand your users' needs and the challenges they face.
2. Identify risks. Assess your designs for elements that could harm or exclude users.
3. Follow best practices. Use WCAG standards and tools like media queries to implement accessible solutions.
4. Test and iterate. Use ethical testing tools to refine your designs based on user feedback.
5. Educate and advocate. Share your knowledge with your team and build accessibility awareness.

This article is adapted from Stefan Chitu’s Improving accessibility for users with epilepsy that appeared on Medium on International Day of Persons with Disabilities (December 3) 2024.