The fat under your eyes is called infraorbital fat. In medical settings, it’s also referred to as orbital fat pads. This fat sits inside your eye socket, just below the eyeball, and is divided into three distinct sections: a medial (inner), central, and lateral (outer) compartment. When this fat pushes forward and becomes visible as puffiness or bags, the condition has its own name: steatoblepharon.
The Three Infraorbital Fat Compartments
Your under-eye fat isn’t one solid mass. In about 60% of people, it’s organized into three separate, encapsulated compartments sitting side by side beneath the lower rim of your eye socket. The central compartment is the largest, spanning roughly 24 millimeters wide. The medial and lateral compartments are each about 17 millimeters wide. All three sit roughly 7 to 9 millimeters below the bony rim of the eye socket.
Each compartment is wrapped in its own thin membrane, which is why under-eye bags sometimes look lumpy or uneven rather than smooth. One compartment can bulge more than the others, creating an irregular contour. The medial (inner) compartment is the one most people notice first, since it tends to catch light and shadow near the nose.
What Holds the Fat in Place
A thin tissue layer called the orbital septum acts like a wall between the fat inside your eye socket and the skin of your lower eyelid. When this septum is firm and elastic, it keeps the fat tucked behind the bone. When it stretches or thins out, the fat pushes forward against the skin, creating visible puffiness.
Research from cadaver dissections shows that the septum doesn’t actually tear or develop holes in most people. Instead, it gradually loses its elasticity, allowing the fat behind it to press outward across the entire lower lid area. Think of it like a hammock that slowly sags under weight rather than snapping. The degree of stretching varies across different parts of the septum, which is why some areas bulge more than others.
Why Under-Eye Fat Gets Worse With Age
A common misconception is that eye bags appear because the fat shrinks or shifts position. The opposite is closer to the truth. CT scan studies comparing age groups show that infraorbital fat volume actually increases with age, particularly after 50. At the same time, the fat becomes less dense, meaning it’s softer and more prone to bulging forward.
This increase in fat volume happens alongside rising body weight and BMI as people age, and both factors contribute to more prominent under-eye bags. Meanwhile, the bone and soft tissue around the eye socket gradually recede, and the skin loses collagen. So you get more fat pushing outward through a weaker barrier, with less structural support around it. That combination is why eye bags tend to worsen in your 40s and 50s even if you’re well-rested and healthy.
Steatoblepharon vs. Tear Troughs
Two terms come up frequently when people research under-eye concerns, and they describe opposite problems. Steatoblepharon refers to the forward bulging of orbital fat, creating puffy bags. Tear troughs are the hollow grooves that run from the inner corner of the eye down toward the cheek. Many people have both at the same time: a puffy bag sitting directly above a sunken groove, which makes the puffiness look even more dramatic by contrast.
The tear trough itself isn’t fat. It’s a depression where the lower eyelid meets the upper cheek, and it deepens as the fat and bone beneath the skin thin out over time. The visual combination of a bulging fat pad above and a hollow groove below is what gives the classic “tired” appearance.
How Under-Eye Fat Is Treated
When under-eye fat bags are prominent enough to bother someone, the standard surgical option is lower blepharoplasty. Surgeons can either remove excess fat, reposition it to fill in the tear trough below, or graft small segments of fat into the hollow areas. A study comparing fat repositioning to segmental fat grafting in 339 procedures found that grafting produced a greater reduction in tear trough depth over an average follow-up period of nearly 13 months, with a smoother transition between the eyelid and cheek.
For people who aren’t ready for surgery, hyaluronic acid fillers injected into the tear trough can camouflage mild to moderate fat pad bulging. The filler doesn’t remove or reduce the fat. It fills in the hollow below the bulge so the transition looks smoother. In one documented case, a single session with 1 milliliter of filler improved both the hollowness and the apparent bulging in a patient with significant tear troughs and prominent fat pads. Fillers are temporary, typically lasting 6 to 18 months before they dissolve.
Neither approach changes the underlying aging process. The orbital septum will continue to thin, and the fat volume may continue to increase. But for most people, a single surgical procedure provides results that last a decade or longer, while fillers offer a lower-commitment option for earlier or milder changes.