Great question. This is a not infrequent complaint that I hear of. The most common reason is that of orbital fat atrophy that occurs as a normal ageing process. Secondary causes include previous orbital trauma, orbital wall fracture, or ptosis (drooping eyelid).
The treatment is primarily to address the root cause (for example, orbital wall fracture repair, orbital volume replacement or ptosis repair). If all other secondary causes are excluded, a straight forward supra-periosteal injection of hyaluronic acid filler or micro-fat injection to the superior sulcus will help to disguise this upper lid sulcus depression to restore a youthful and fresh appearance.
Best of luck with the treatment choice that you make!
ESG