The neurological basis of visual discomfort and visual stress

Visual entertainment enriches our daily lives, but some visual features can also induce visual discomfort and even more serious adverse effects. A well-known example is the 1997 “Pokémon Shock” incident in Japan, in which hundreds of viewers experienced symptoms including seizures following exposure to rapidly alternating red and blue flicker. Motivated by this incident, we have investigated the visual features of flickering patterns that evoke discomfort. Our findings indicate that flicker patterns that deviate from temporal structures and chromatic distributions commonly found in the natural visual environment tend to be experienced as more uncomfortable. We have recently extended this approach to motion artifacts in visual media. When animation and film content is presented at a relatively low frame rate, motion can appear jerky, a phenomenon known as judder. Unlike flicker, judder is primarily a motion artifact, yet it is also a visual feature that is rarely encountered in natural viewing. By systematically manipulating lightness, contrast, and motion displacement, we found that visual discomfort tended to increase with the perceived strength of judder. These findings suggest that deviations from characteristics of natural visual input may provide a useful framework for understanding visual discomfort across different types of visual stimulation. This work may contribute to the development of safer and more comfortable visual environments, while maintaining the intended perceptual quality of visual content.

Dr Sanae Yoshimoto

University of Hiroshima, Japan

Dr Sanae Yoshimoto

University of Hiroshima, Japan

Sanae Yoshimoto is an Assistant Professor in the Graduate School of Humanities and Social Sciences at Hiroshima University. She obtained her PhD from Japan Women’s University and subsequently worked as a postdoctoral researcher in the Department of Psychology at the University of Nevada, Reno. Her research investigates the underlying mechanisms of visual discomfort, with a particular focus on how visual features such as temporal and chromatic properties influence subjective discomfort. She has recently begun examining visual discomfort and its relationship to other forms of negative affect, combining psychophysical experiments, physiological and neural measurements, and computational approaches.

Flickering lights can induce headaches, seizures, discomfort, and illusions. Light emitting diodes (LEDs) can flicker and are widely used in homes, schools, offices, and cars. The brightness of LEDs can be controlled through pulse-width modulation, which generates temporal light modulation (TLM), at higher frequencies than standard mains electricity. This poses a potential problem because the visual system can resolve high frequency TLM (up to 15kHz) during saccades - the flicker appears as an illusory striped pattern known as the phantom array. The question then, is what are the effects of high frequency TLM on visual processing? We recently found that TLM at 600Hz can slow reading, particularly when individuals report high pattern glare. However, reading speed was slightly faster when under 120Hz (US AC rate) TLM compared to neighbouring frequencies, suggesting some adaptation to common frequencies that limits the negative effects. In addition, there was no relationship between the ability to detect the phantom array and reading speed. This suggests that TLM disrupts visual processing independently of conscious perception. LED TLM is currently unregulated (the IEEE guidelines lapsed March 2026), and these findings support calls for new regulations on lighting to mitigate the effects of TLM on health and cognition.

Dr Sarah Haigh

University of Nevada, US

Dr Sarah Haigh

University of Nevada, US

Dr Haigh is an Assistant Professor in Psychology and Neuroscience at the University of Nevada, Reno. She obtained her PhD from the University of Essex, then completed post-doctoral training at Carnegie Mellon University and the University of Pittsburgh School of Medicine in the US. Her lab investigates the effects of sensory discomfort on neural functioning and behaviour, and the individual differences in these effects in clinical and neurodiverse populations. Her goal is to reduce, and eventually eliminate, the adverse effects of sensory discomfort on complex behaviours and health.

Visual discomfort is commonly approached through the characteristics of the visual stimulus and the neurological and perceptual mechanisms through which it is processed. Yet these stimuli are rarely encountered in isolation. For most people, prolonged visual exposure occurs within designed environments whose spatial configuration, materiality, lighting, colour, pattern, contrast and environmental conditions collectively shape visual experience.

This talk considers visual comfort from the perspective of architecture and urbanism, examining how characteristics of the built environment may contribute to, intensify or mitigate visually stressful conditions. It explores the relationship between environmental design and human experience across different spatial scales, from architectural settings to the wider urban environment, with particular attention to contexts in which strong sunlight, glare, reflection and high visual contrast are recurring features of everyday experience.

Drawing on research concerned with environmental design, sustainable urbanism and human responses to the built environment, the talk will consider how knowledge emerging from neuroscience and vision science might be translated into design thinking. It will also identify opportunities for greater interdisciplinary collaboration between neuroscientists, vision researchers, architects and urban researchers. Such collaboration could help move visual comfort beyond a largely qualitative design consideration towards a more evidence-informed understanding of how environments can be designed to reduce unnecessary visual stress while supporting wellbeing, accessibility and positive human experience.

Dr Fay Abdulla Al Khalifa

University of Bahrain, Bahrain

Dr Fay Abdulla Al Khalifa

University of Bahrain, Bahrain

Dr Fay Abdulla Al Khalifa PhD FHEA is an Associate Professor of Architecture and Urbanism in the College of Engineering at the University of Bahrain. She holds a PhD in Urban Sustainability and an MA in Conservation and Regeneration from the University of Sheffield, UK, and a BSc in Architecture from the University of Bahrain. Her research focuses on the relationship between the built environment and human experience, with particular interests in sustainable urbanism, smart and sustainable cities, environmental design, urban liveability and climate-responsive environments. Her work has examined how physical and environmental characteristics of buildings and cities influence human perceptions, behaviours and quality of life, particularly within the climatic and cultural context of the Arabian Gulf. Alongside her academic career, she has held several senior institutional leadership roles at the University of Bahrain, including Director of the Quality Assurance and Accreditation Center and, previously, Director of the E-Learning Center. She is also President of the Bahrain Smart City Society.

Humans are embodied beings whose sensory systems evolved over hundreds of thousands of years to guide action in natural environments. Today, however, most everyday settings differ markedly from the woodlands and savannahs of our ancestors. In this talk, I will argue that this mismatch generates sensory challenges our brains and bodies are poorly adapted to handle. In particular, visual difficulties can arise when design features that once signalled survival-critical information—such as repetitive, high-contrast striped patterns—become abundant yet behaviourally irrelevant in modern spaces. These features degrade the signal-to-noise ratio for visual processing, increasing uncertainty in vision-based decisions that guide movement and behaviour. Evidence comes from studies measuring gait kinematics and visual discomfort as people walked through different visual environments, and from experiments testing cognitive performance against task-irrelevant visual backgrounds. Beyond laboratory work, I will present a case study in which we co-created with designers a virtual-reality test space of a new building project in its planning stages to predetermine the potential negative sensory impact of alternative design decisions. The talk concludes by touching on the challenges of translating scientific insights about human visual perception into practical guidance for architects, designers, and planners seeking to create healthier, more comfortable, and inclusive places.

Professor Ute Leonards

University of Bristol, UK

Professor Ute Leonards

University of Bristol, UK

Ute Leonards is a Professor of Neuropsychology at the School of Psychology and Neuroscience, University of Bristol, UK, with a primary research interest in human vision in the context of everyday life. Why vision? Because what we see guides our movements, shapes our experiences and thoughts, influences how we interact with others, and ultimately defines who we are. Who we are defines what we see and how we see it. Ute’s transdisciplinary research collaborations have helped to inform disparate societal challenges such as international tobacco control policy and legislation since 2011 and recent guidance for inclusive design by the British Standard Institute (BSI PAS 6463-2022).

Visual stress (VS) is increasingly used to describe abnormal visual discomfort and perceptual distortions in response to specific visual stimuli. This review uses a staged evidence-synthesis approach: an initial systematic review that identifies minimal core evidence is followed by a scoping review to map broader literature, and a narrative synthesis to integrate diverse sources.

Systematic review: PubMed/PsycInfo/Web of Science were searched for “Visual Stress” OR “Visual Discomfort” AND “Differential Diagnosis” revealing, five manuscripts. Four of these were relevant but none met the selection criteria (specification of: condition of interest, competing diagnoses, target population, and clinical verification method).

Scoping review: to determine the broader literature that might be relevant to differential diagnosis of VS. Key publications were used to identify the main symptoms and clinical signs of VS and the literature (including “grey sources”) was searched for other conditions associated with these symptoms and signs.

Narrative review: the third stage was a narrative review to estimate the likelihood of these conditions being mis-diagnosed as VS. Risk matrix methodology was used to juxtapose, for each condition, the probability of the condition being present with the severity/impact arising from an incorrect diagnosis of VS.

Overarching conclusions: highlight, for clinicians who diagnose and treat VS, the alternative diagnoses that need to be excluded. Conclusions will also consider, for researchers investigating VS, sensible precautions to maximise the probability that findings relate to VS and to demonstrate that the researchers have taken reasonable steps to avoid participant harm through erroneous diagnoses.

Professor Bruce Evans

City St George's University of London, UK

Professor Bruce Evans

City St George's University of London, UK

Bruce Evans has practised as a community optometrist for over 40 years and is Visiting Professor to City St George’s, University of London; London South Bank University; and University of Milano-Bicocca, Milan. From 1998-2023 he was Director of Research at the Institute of Optometry. He is a Fellow of: College of Optometrists, American Academy of Optometry, European Academy of Optometry, and British Contact Lens Association. He has authored >280 scientific and CPD papers, 10 editions of optometric textbooks, >160 presentations at scientific conferences, and >500 invited CPD lectures. His main areas of research are myopia control, binocular vision (orthoptics), dyslexia and vision, visual stress, children’s vision, contact lenses, computer vision syndrome, and headaches. In 2022 he was awarded Life Fellow of the College of Optometrists in recognition of outstanding contribution to the optometric profession, and in 2023 a Lifetime Achievement Award of the Association of Optometrists.