"So That's What You See": Building Understanding with Personalized Simulations of Colour Vision Deficiency
David R. Flatla, Carl Gutwin · 2012 · Proceedings of the 14th International ACM SIGACCESS Conference on Computers and Accessibility (ASSETS 2012) · doi:10.1145/2384916.2384946
Summary
This paper presents a personalized colour vision deficiency (CVD) simulation method that shows people with normal colour vision what a specific individual with CVD actually sees, rather than relying on generic models. Existing simulation tools like Vischeck have three key limitations: they only simulate dichromacy (the severe form where a cone type is completely missing), which is too extreme for the 75% of genetically-caused CVDs that involve anomalous trichromacy (where cones are shifted rather than absent); they require users to know their specific CVD type, which most do not; and they can only simulate one CVD type at a time, missing cases where individuals have multiple deficiencies (common in acquired CVD from aging, cataracts, or chemical exposure). The personalized approach uses empirical calibration to measure each individual's actual colour differentiation abilities through a gapped-circle test that identifies discrimination limits along six colour lines in CIE L*u*v* perceptual colour space. This creates a discrimination ellipse unique to each person, capturing both the type and severity of their CVD. The method then performs a partial dichromatic simulation — shifting colours along confusion lines by the measured amount rather than all the way to the dichromatic half-plane — producing an accurate representation of that specific person's colour perception.
Key findings
Quantitative evaluation showed personalized simulations were significantly more accurate than standard dichromatic models (p<.01), with calibration measurements only two "just-noticeable steps" away from CVD participants' actual discrimination limits. A qualitative study with five pairs (one CVD person + one close friend/family member) exploring 16 everyday images produced striking revelations. Even long-term couples and friends gained new insights: non-CVD partners expressed shock that unripe bananas and ripe bananas looked identical in the simulation; the inability to see pink in raw meat prompted reactions like "I'm not letting you barbecue anymore!"; rainbow simulations reduced to two bands of colour prompted a CVD participant to exclaim "That's how they have always looked to me!"; and a non-CVD partner finally understood why her partner hated yellow ("It's too bright!"). Safety implications emerged when CVD participants described coping strategies for traffic lights (relying on position rather than colour). Post-session questionnaires showed non-CVD participants rated their understanding 0.9 points higher on a 7-point scale after using the personalized simulations. CVD participants also benefited, learning how their partners perceived colour and gaining vocabulary for future communication about colour differences.
Relevance
This paper makes a profound contribution to accessibility by addressing the empathy and understanding gap between people with and without CVD. For accessibility practitioners, the work demonstrates that personalization matters — generic simulations of disability experiences can be misleading because they typically represent the most severe cases rather than the spectrum of actual experiences. The personalized approach is applicable beyond CVD to any condition where perception varies individually, such as low vision, hearing loss, or cognitive differences. For designers, the paper reinforces that colour-dependent information (food ripeness indicators in apps, status colours in dashboards, colour-coded maps) creates real barriers for the 8% of men and 0.5% of women with CVD. The finding that even close family members gained significant new understanding after years together underscores how invisible perceptual differences can be, and how powerful well-designed simulation tools can be for building empathy and awareness. The suggestion of a "community of simulations" where designers could test their work against multiple real CVD profiles remains a compelling vision for inclusive design practice.
Tags: colour vision deficiency · color blindness · simulation · personalization · anomalous trichromacy · dichromacy · empathy · colour perception · calibration · accessibility awareness