Hi,

I'm going to be involved in a project involving a website for the visually impaired, so I'm researching all aspects of building such websites,

From what I heard so far, people use software that takes the content of a website and turn it into vocal output (in other words dictate it) , and therefore pages in such a website should contain mostly text and no images or other junk that might interfere with translating the content into vocal output

If anyone has information about such and about optimizing websites for the visually impaired population, feel free to contribute

You should have a nice clean layout. Preferably structured as a book.
Use headings <hn></hn> and paragraphs, making the pages in valid XHTML/HTML/CSS would be great. http://validator.w3.org
Not too many images as you said, and Don't use iframes.

There's more information on the w3 website http://www.w3.org/WAI/
Remember, you are not only making your pages easy to read for the visually impaired, but for all internet users therefore creating a better world for all of us!:)