If it's Circulatory darkness (blue-ish purple present in the inner corner mostly) then I would recommend either the B. Kamins Therapeutic Eye Cream, or Peter Thomas Roth Power K. They both have an enormous amount of Vit. k which helps to repair capillary walls which leak blood in the first place, causing darkness to be visible.
If it's Hyperpigmentation, you want to look for Vit. c, and I would recommend the MD Skincare Lift and LIghten (a great choice if you're not sure which you have) or the Murad Essential C eye cream (with SPF15!) Keep in mind it will take about a month or more to see results from either of the mentioned creams. BE PATIENT!