Visual stress is more common in dyslexics than in the general population. It is a sensitivity to patterns, especially high contrast lines or stripes, which can cause visual perceptions or distortions. These patterns can be the individual words or lines which make up a paragraph. Words may appear to move, blur or change in size or shape.
People can also become hyper-aware of gaps between words ‘linking up’ and appearing as rivers down the page. This can lead to fatigue when reading, missing words or complete lines, and re-reading the same line again.
Evidence is limited but Visual Stress can be alleviated with the use of a coloured tint, specific to that person. Initially, overlays are used to determine whether colour does indeed help the patient, then if so, the patient can choose whether to have Colorimetry.
A Colorimeter is a machine designed to pinpoint the correct hue and saturation of tint for maximum reduction of the symptoms of visual stress. Visual stress can also occur in non-dyslexics, and in both cases symptoms can become more apparent under pressure, such as reading out loud, revising for, and being in exams.