Many believe that dyslexics switch letters within a word, or write words backwards. This does happen, but only for the smallest minority. Most often dyslexia comes out in the form of mistaking similar looking letters for each other, leading to inadvertent substitutions of an incorrect, but similar looking word:
A lower case d is an upside down p. The mind flips it. An h is very similar to an n. The lower case e is a lot like an upside down a.
Apart from visual similarity amongst letters, English is rife with exceptions, irregular spellings, and multiple pronunciations for a given letter (or combination of letters), compared to Spanish, for instance. The technical term for this is orthographic depth. English has a deep orthography, making it a greater challenge for dyslexics.
The Dutch firm Studiostudio has designed the font Dyslexie, in which differences in letters are emphasized. Openings, slant and extensions are exaggerated - a bit. Letters look heavier at the bottom, so it's harder to rotate them in the mind's quick processing.
Here's a two minute film showing how all of this works.
Research done at the University of Twente showed that dyslexics made fewer reading errors using this font. According to a comment on the youtube page for this clip by Christian Boer of Studiostudio, they're working on making Dyslexie available for sale internationally. At some point we'll be able to have it on our computers, read the internet with it, send email in it, maybe even put downloadable books into it.
It's estimated that five to ten percent of the world population suffers some degree of dyslexia, though these numbers are unconfirmed. The condition has nothing to do with intelligence. Dyslexia.com provides a list of famous dyslexics which includes Albert Einstein, John Lennon, Winston Churchill, Agatha Christie, Henry Ford, Whoopi Goldberg, Pablo Picasso, Leonardo Da Vinci, and many others.
Here's hoping Dyslexie catches on, and perhaps even becomes a default font. It would make a big difference in many lives.
For further information and news on Dyslexie, visit Studiostudio's website.