This is something I had also read about in a few places, in the past. My husband also says he can sometimes see mania in my eyes. I first read about it in Wikipedia's entry on mania. It includes the line:

"Other, often less obvious elements of mania include... the eyes of such patients may both look and seem abnormally "wide open", rarely blinking, and may contribute to some clinicians’ erroneous belief that these patients are under the influence of a stimulant drug..."