The presence of under-eye darkness is a frequent complaint that is more commonly associated with upper cheek depression than orbital hollowness. Skin discoloration (as opposed to shadowing of a tear trough) is caused by an increase in the amount of skin pigment (melanin).
The most common determinant is heredity, but any irritant that causes chronic tissue swelling (allergy, fluid retention, eyelash infection, rubbing, sun exposure, metabolic imbalance, medications such as birth control pills, etc.) may contribute. In cases of increased melanin deposition, blepharoplasty or fat grafting surgery will not improve on the discoloration.

What Can Help?
Bleaching creams, gels, and solutions may interfere with creation of new melanin are sometimes useful. They are available in a variety of formulations and strengths (some over-the-counter and some only by prescription) and may cause skin or eye irritation. Since any improvement is usually modest and only seen very gradually over several months, many patients quit treatment prematurely.
Since a "side-effect" of skin resurfacing is often a slight loss of pigmentation in the treated skin, some patients with naturally lighter skin tones may benefit from chemical peel or laser resurfacing.
In the absence of a medical cause or anatomical problem, cosmetics offer the most effective and safest option. A good concealer (examples: Dermablend, Covermark) can do wonders at hiding dark circles. Consultation with a cosmetologist is often helpful.

What To Do About Those Dark Circles