Therefore, use of a dynamic braille display is an important and effective option. Although there are a number of assistive technologies available in each of the above categories, the effectiveness of these assistive technologies in providing access to an electronic textbook is dependent upon the design of the electronic textbook. Information which is not available in text form, for example, cannot be displayed using speech or braille. Software which requires an individual to simultaneously monitor two events occurring at opposite edges of the screen would be difficult for someone to operate by using screen magnification. It is not necessary, however, to limit electronic textbooks to purely text presentation in order to make them accessible.
Strategies exist for making even richly graphical systems accessible.