The thin and highly flexible eyelid skin is rather unique in the body in that it lacks a subcutaneous fat layer found typically in almost all other skin. What is often called "eyelid fat" is, in fact, not really from the eyelid at all. Instead, orbital fat located deep inside of the bony socket extends normally forward into the eyelid as "fat pockets." If too much orbital fat projects forward, the unsightly bulge pushing out against the eyelid may lead a patient to seek blepharoplasty.
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Cross-Section of Eyeball in Socket
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As shown in the diagram at left, the eye sits inside of a bony socket, which encloses a space known as the "orbit." In addition to the eyeball, the orbit contains an array of tiny muscles, nerves, and blood vessels that allow the eye to function.
Surrounding these structures sits the orbital fat, a sort of padding that cushions, protects, and holds all of these delicate structures in their normal positions inside of the socket and helps them to relate properly to one another.
Likewise, the orbital fat pushes out against the eyelids and helps to stabilize the lids in their proper positions.
Any process that disturbs or depletes the orbital fat is thus bound to have negative consequences on both the eye and the eyelids.
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Eyeball
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Orbital Fat
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Eye Muscles
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Socket Bone
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The cross-section of the socket shown above bears a remarkable resemblance to a fully inflated tire with its metal rim sitting squarely at its center. In the analogy that follows, think of the rim as the eyeball, the rubber of the tire as the eyelid, the space inside the rubber as the orbit, and the air filling up this empty space as the orbital fat.
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Clearly, both the rim and tire rubber are dependent upon the presence of a proper amount of air pressure to maintain normal position, shape, appearance, and, of course, function.
Now, imagine the consequences of a large loss of air (fat) from the inside of the tire (orbit) after a blow-out (for instance, overdone lower blepharoplasty):
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Normal Volume
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• The entire structure immediately loses it shape and sags.
• The rim of the tire drops lower as its support becomes depleted.
• The rubber comprising the bottom of the tire (lower eyelid) collapses downward under the weight of the rim and becomes buckled.
• The rubber comprising the top of the tire (upper eyelid) is no longer held firm by air pressure and so not only grows flaccid but lifts upward and off the dropped rim (a higher and hollowed eyelid crease).
• While the car may continue to lurch haphazardly forward for a short distance, in doing so the tire may become rapidly more damaged. Eventually, the car either comes to a halt or has an accident.
• Regarding appearance, well... a flat tire is always a sad sight.
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Volume Depletion
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The first thought through the driver's mind is to open the trunk and get out the spare (unfortunately, no equivalent exists in this analogy). Even if the spare is missing, a new tire is just a short tow and a hundred dollars away (again, no equivalent for the eyelid).
What else might be done? Building up the thickness on the front side of the crumpled rubber (injecting commercial fillers or liposuctioned fat) might temporarily make the collapsed tire appear less damaged but that would do nothing to restore it to a usable state.
Shaving off a chunk of crumpled rubber to make the tire smoother (skin removal) would be worse yet and ruin any chance of ever salvaging the flat.
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If the tire is not terminally damaged, the obvious best thing to do is apply a patch and reinflate.
More than anything else, what is needed to make a flat tire whole again is to have the right amount of air pumped deep inside (orbital fat grafting) to restore volume and pressure and function.
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When orbital volume depletion occurs after aggressive fat removal during lower blepharoplasty, similar changes and potential remedies exist for the eyelid. Thus, we have found it both instructive and highly descriptive to name this syndrome "the orbital flat tire."
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