![]() However, filtering may also drastically affect visual perception. Within the visual spectrum, this color is the one with the longest wavelength and it can be easily eliminated by wearing appropriate optical filters (blue lenses). Certain colors are critical in particular, the so-called saturated “deep” red. More of the visual field is occupied therefore, more of the brain gets stimulated. For instance, going back to the example of television viewing, the closer the person gets to the screen, the greater the risk. One is the viewer’s distance from the light source because it directly affects the field of vision. There are other factors involved, as well. About 30 percent of individuals sensitive to lights are also sensitive to patterns. The consensus recommends no more than five pairs of stripes if they are moving within the field of vision and no more than eight pairs if they are static. The danger depends on how many and how contrasted the stripes are in the visual field. Static or moving patterns of discernable light and dark stripes have the same effect as flashing lights because of the alternation of dark and bright areas. This also explains why most affected individuals can prevent the photosensitive reaction by simply covering one eye (monocular vision). For instance, in the case of television viewing at a distance of about nine feet, the consensus recommends the area of the flashing stimulus on the screen be not greater than 25 percent of the total area. This is important because it actually determines how much of the brain gets stimulated.
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