Anatomy of the facial skin
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The eyelid skin is quite different from other facial skin in that it is (1) much thinner and (2) essentially devoid of a normal subcutaneous fat layer. What is often referred to as "eyelid fat" is actually an extension of the orbital fat -- that is, the fat filling the orbit that cushions the eyeball in its socket. Diagrams
For facial skin other than on the eyelids, fat injected through a needle can be distributed into the deeper dermis, existing subcutaneous fat layer, and into or below the underlying muscle.
It is, however, very difficult to inject liposuctioned fat into its proper anatomic location in the orbit without risking injury to the eyeball and its surrounding blood vessels and muscles. Furthermore, injection techniques require many passes of the cannula to achieve a layering of pencil-thin cores of fat tightly surrounded by normal tissue. Because of the fragile and flexible nature of orbital tissue, injected fat instead tends to pool and not achieve the apposition needed for fast revascularization and survival.
If fat is injected into or just under the thin skin of the eyelid, it may disappear quickly or form visible lumps that are especially noticeable when a patient smiles or squints and interfere with normal draping of the eyelid skin over the crease. |
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