Now that iOS 7 is out, here is how I have my iPad set to assist with my vision disability.

Fist, the clean and lots of white space are very good for my vision. There is very good contrast between text and background and that is necessary for me. Otherwise, there are only two things I've changed to make things really work for me.

Enlarge the font
Make the text bold

I just need larger text to be able to read and the iPad does this very well. The newly advertised "clean" interface is really good but a bit thin for me so I just make the text bold.

All necessary changes are done in Setting > General > Accessibility

Turn Larger Text to On.
The next page has the slider adjustment to the desired text size.
Then turn on the Bold Text.

Once Large Type is turned on, I slide the slider bar to the right to the desired size. As you can see, I use one step down from the largest text size.