I have pretty good vision and even as I approach my mid-30's do not need glasses or contact lenses.  All is not peachy though -- reading light text on dark backgrounds causes me pain about a paragraph or two into reading an article.

A solution, which a friend recently pointed out to me, is to 'Reverse black and white' as Apple calls it by holding down crtl+option+command+8.  As you have probably worked out this switches the black and white and allows me to read entries without my eyes hurting.

I tried taking a screenshot but Apple takes a screenshot of the orginal settings not the reversed.