This is from the January 2012 issue of Oprah magazine.

Here’s an eye-opener: For years studies have shown that flavonols, the antioxidant-rich compounds found in cocoa, improve circulation. Now new research indicates that because those compounds increase blood flow to the brain, they may also help you see more clearly. Two and a half hours after consuming 720 milligrams of flavonols (the amount in about one ounce of dark chocolate), study participants’ visual function and ability to detect motion direction improved dramatically.