Being a dyslexic pilot and flight instructor myself, I know that it is not an issue. I have a 1st class medical, no restrictions. Dyslexia can run in many different forms. My father for example had speech issues, I have spelling issues, my sister had reading issues. By the way dyslexia is hereditary. Dyslexia can be overcome; it just takes time and work. As an instructor you may have to find a different way to present the information and a different way for the student to practice skills. Some dyslexics will have problems with sensorial overload. For example “Squak 0341, descended to 3500, turn right to 300 and contact approach on 127.3, good day” This would overload most students, and many pilots alike, but a dyslexic may have more problems with all this information be presented at once.
As for dealing with dyslexia Albert Einstein, Henry Ford, Thomas Edison, Alexander Graham Bell, Leonardo da Vinci, Nelson Rockefeller, Charles Schwab, General George Patton, Winston Churchill, Woodrow Wilson all seemed to do well being dyslexic.