I read a paper that talked about the difference between dyslexic reading and normal reading. The researchers found that dyslexic people actually see too much at once and that by forcing them to focus on a smaller region of text (by, for example, having them read through a small hole in a piece of paper), they had much better performance. With consistent drills, they could even read without the mask.

edit: http://courses.csail.mit.edu/6.803/pdf/geiger1992.pdf