• By your late thirties or early forties, the extremely thin skin of the eyelids starts to lose its elasticity and stretch. In the upper eyelid, this causes the crease to become daped by the overhang. As the collagen in the dermis starts to be lost, the epidermis comes to exist in "relative excess" and wrinkles and crow's feet appear in those parts of the eyelids that move the most. Thinning of the skin may cause an "unveiling" of the underlying oribtal fat, even without true fat bulging.
• Facial fat begins to absorb, leading to volume loss. The resulting deflation not only accentuates the appearance of sagging skin, but may, in some cases, be its primary cause.
• The orbicularis muscle thins out, stretches, and becomes less powerful, contributing to sagging of the overlying skin.
• The eyelid support system starts to thin and then stretch under the influence of gravitational forces, the wear-and-tear of blinking, and certain environmental factors, most notably smoking and excessive sun exposure.
• Deeper fat pockets from the socket may become visible and bulge forward due to a weakening of an eyelid restraining layer (the "orbital septum").
• In some patients, orbital fat inside the socket may absorb rather than bulge, leading to a hollowed appearance in both upper and lower eyelids.
• Much later (not in your thirties!), the frontalis muscle may sag, thus lowering the brow, which in turn pushes the already excess eyelid skin into a more noticeable roll.
• The soft tissues of the cheek and midface (fat, muscles, fascia) begin to lose tone and descend, causing a small area of depression to become exposed below the lower eyelid (the "tear trough"), accentuating any lower eyelid imperfections, and allowing the edge of the orbital rim to show through the skin (a change known as "skeletonization", which, quite fortunately, sounds more scary than it really is).
• In some patients, a triangular area of fluid accumulation may develop in the tissues overlying the bone at the lower outer corner of the lower eyelid ("malar mound"). Such swelling is often variable day-to-day, may take on a purplish color, and often increases after high salt intake.
