Understanding the subtypes of visual hypersensitivity: Four coherent factors and their measurement with the Cardiff Hypersensitivity Scale (CHYPS).

Subjective visual sensitivity or discomfort has been reported in many separate literatures, and includes a wide range of visual triggers (e.g., repeating patterns, bright lights, motion, flicker) across a wide range of neurological, psychiatric, mental health, and developmental conditions and areas of neurodiversity (e.g., migraine, traumatic brain injury, functional neurological disorder, PPPD, PTSD, anxiety, depression, anorexia, OCD, autism, ADHD, dyslexia, dyspraxia, synaesthesia). To unite this research across disciplines and to allow progress in mechanistic understanding, we aimed to provide a definitive answer to whether there are different subtypes (factors) of visual hypersensitivity. In Study 1, we generated questions from a large qualitative dataset (n = 765), existing literatures, questionnaires, and iteratively from participant feedback. We found four theoretically coherent factors replicated across five cohorts (n's = 349, 517, 349, 417, 797 and 1817). These factors were: brightness (e.g., sunlight), repeating patterns (e.g., stripes), strobing (e.g., flashing, screen motion), and intense visual environments (e.g., supermarkets, traffic). There was also a general factor. Based on this we produced a novel 20-item questionnaire (the Cardiff Hypersensitivity Scale, CHYPS), with good reliability (α > 0.8, ω > 0.8) and convergent validity (correlations with other visual scales r > 0.6). We discuss how these factors can be related to causal theories of hypersensitivity.