A few weeks ago I found that I was getting a bit of eye-strain after viewing AB for a while because it's black text on a pure white background. I have solved the problem for myself by using a Firefox add-on and find it so much easier on the eyes to have a less bright background.
Have you considered giving an option within the user profile that would provide an alternative site colour scheme that is easier on the eyes for those viewing AB for a prolonged period?
As you can see it looks quite murky because I decided to keep things simple and just reduce the luminosity of both foreground and background - I very much doubt that it's the type of look that you'd be after but I quickly got used to it and am happy to carry on with it.
To me the lack of contrast makes it very hard to read. I can understand that if you were in a low-lit room it would probably be easier though.
We considered a kind of "easy reader" version with larger texts and a different style. But, as I said, it's never quite made it to the top of the pile.