If a piece of information could be inaccessible to someone, always convey that information in a second format. This information is shown in both text and picture.
The golden rule for this course is: If a piece of information could be inaccessible to someone, always convey that information in a second format.
It is important to remember that what is good for one person can be bad for another. Having a simple diagram to explain a procedure will be great for a person who has dyslexia, but useless for someone who has low vision. So make sure the relevant point is explained in the text as well.
For example, if you have an audio voiceover on a Web page for people who are blind or dyslexic, make sure that you also have the text available for people who are deaf. This does not mean that you have to rush out and create audio tracks for every Web site; if you have a textual document and the text is totally accessible, then that document is complete. Text is always the default; as you will find out later, text can be accessible for everyone.
By having information available in more than one form, you are giving your readers more opportunities of having the information in a format that is suitable for them. And giving yourself a better chance to communicate with those people.
You should not try to design a document that is suitable only for one group of people, for example, people who are blind. Instead, you should write documents that are suitable for everyone.