This page gives an overview of screen readers and talking browsers
There are specialist browsers that can combine hi-visibility features with speech output to cater for those with little or no vision.
One such program is IBM's Home Page Reader. It presents all web pages in an uncluttered text-only view and speaks out all text, links and picture tooltips.
IBM's Homepage Reader
It allows text to be made much larger than is possible in standard browsers, and uses colour as well as size to indicate different screen elements.
Windows' Narrator is a limited speech output program and not a complete solution, for example, for those with no useful vision.
For a blind computer user to have effective access to MS Word, Internet Explorer and all the many other programs they may want to use a full screen-reader. Examples include Jaws and Window-eyes.

JAWS screen-reading software
These packages can be quite expensive but offer a lot of features such as reliable speech output which is essential for effective access for a blind user.