We want to make computers work for everyone, whatever your physical circumstances. So, we provide tools that make Ubuntu one of the most accessible operating systems around.
You can get at these tools in one place: the Assistive Technologies Preferences, inside the System Menu. From there, you can turn on helpful tools like Orca, to speak text on the screen, or dwell click to press mouse buttons automatically.
Remember to check out the Appearance Preferences, too. You can choose between different visual styles and even change the fonts that are used by applications.

Accessibility in Ubuntu