However some kinds can be corrected like visual problems. I know a guy with dyslexia who uses very specific, slightly tinted (towards green) lenses in his glasses. I can't remember what else was different about them, but basically they were very personalised and had the effect of slowing down the eye movement over the text. (as in, it forced him to track the lines normally instead of jumping around) Based on chat experience, they made a lot of difference.