Achromatopsia

A rare inherited vision condition in which a person has little or no ability to perceive color, seeing the world primarily in shades of grey. People with achromatopsia typically also experience light sensitivity (photophobia), reduced visual acuity, and involuntary eye movements (nystagmus). In digital accessibility, achromatopsia is one of the most severe forms of color vision deficiency and underscores why information should never be conveyed by color alone — designers must provide redundant cues such as text labels, patterns, icons, or shape differences to ensure content is distinguishable without color perception.