Visual stress: origins and treatment

The statistical characteristics of visual images that provoke discomfort generally differ from those of images found in nature. Computational models of the cortex suggest that uncomfortable images are processed inefficiently, a suggestion consistent with the large electrical and haemodynamic cortical response such images induce. The response is greater in individuals who customarily experience visual discomfort, such as those with migraine. Text provides an unnatural image and can be uncomfortable when small and closely spaced. It can provoke illusions of color, shape and motion, just as do patterns of stripes, and these illusions can disturb reading and reading acquisition. Changing the lighting chromaticity can sometimes reduce these illusions, particularly in patients with migraine aura, thereby facilitating reading.