Dark circles in Busan Seomyeon, and why filler is only right for one of them.

Patients arrive asking for under-eye filler more often than for any other single treatment, and it is the right answer for roughly a third of them. The other two thirds would be worse off — sometimes considerably — which is why the examination happens before the treatment is discussed.

Cause one — hollowing

A genuine loss of volume in the tear trough, where the ligament tethers skin to bone and the fat pad above has thinned. The shadow is anatomical: light falls into a depression. This is the version under-eye filler is designed for, and where it produces the most striking results of any treatment in the area. It is also the least common of the three in patients under forty.

Cause two — pigmentation

Melanin deposited in the skin of the lower lid, often genetic and more common in Asian and Middle Eastern skin. The area is darker rather than deeper, and the colour is brown rather than blue-grey. Filler here does nothing to the colour and adds volume beneath pigmented skin, which frequently makes it look worse. The treatment is low-energy toning, patiently and across several sessions.

Cause three — thin skin and visible vessels

Skin under the eye is the thinnest on the body, and where it thins further with age the underlying vessels and orbicularis muscle show through as a blue-grey cast. Nothing is hollow and nothing is pigmented — the problem is transparency. Filler here produces the puffy blue appearance patients describe, because hyaluronic acid under thin skin scatters light. The answer is thickening the skin with Rejuran Eye rather than adding volume beneath it.

How do I tell which I have?

Two tests, in a mirror. Tilt your head back toward the ceiling and look at the reflection — if the shadow lightens or disappears, it is hollowing, because you have removed the depression from the light path. Then stretch the skin gently sideways with a finger — if the colour stays, it is pigmentation; if it fades, it is vascular or shadow. Between them these two tests sort most patients correctly before any consultation.

Why does filler go wrong here so often?

Because the under-eye punishes error more than anywhere else. The skin is thinnest, the tissue holds water readily, and hyaluronic acid placed too superficially produces the Tyndall effect — a blue cast from light scattering through the gel. Too much volume produces persistent puffiness that patients mistake for swelling and wait months to resolve. This area needs the least product of any on the face and is where more is most often given.

Why is this the most misdiagnosed concern we see?

Because the patient arrives with a treatment name rather than a symptom, and the treatment name is almost always filler. Under-eye filler is the most searched cosmetic treatment for this area, so patients read about it, recognise their own shadow in the description, and book it. The three causes are indistinguishable in a photograph and nearly so in a mirror without the two tests above — which means a clinic that takes the request at face value will treat the wrong thing roughly two times in three without anyone intending to.

What does a proper under-eye assessment involve?

Four things, none of which take long. The head-tilt test to identify hollowing. The skin-stretch test to separate pigment from vascular. An assessment of skin thickness by gentle pinch, which decides whether a booster belongs in the plan. And examination for fat pad herniation, since a bulge above the trough changes the answer entirely. Only after those four does a treatment get named — and sometimes the honest conclusion is that laser is the answer to something the patient came in wanting injected.

What if I have more than one cause?

Most patients over forty do, and the sequence matters. Pigmentation is treated first with toning, since it takes several sessions and improves what you are looking at. Skin thickening follows if transparency is a component. Volume goes last, and usually less of it is needed than the initial assessment suggested, because the first two steps changed how the shadow reads. Treating volume first is what produces overfilling.

What can be fixed and what cannot?

Hollowing responds well and predictably. Pigmentation improves substantially over a course but rarely clears entirely, particularly where it is genetic. Thin skin thickens measurably but does not become thick skin. And structural shadow from the orbital rim itself — a deep-set eye socket — is anatomy rather than a condition, and no injectable changes bone. Being told which category you are in is more useful than an optimistic estimate.

What about the puffiness under the eye?

A different problem again, and one that filler actively worsens. Fat pad herniation — the bulge above the trough rather than the hollow below it — is surgical territory, and adding volume beneath a bulge makes the whole area heavier. Fluid retention responds to sleep, salt and position rather than to treatment. Distinguishing bulge from hollow is part of the examination and changes the answer entirely.

What if I already had filler and dislike it?

It is reversible, and quickly. Hyaluronic acid dissolves with hyaluronidase within a day or two, and the area can be reassessed a fortnight later once everything has settled. Bring whatever records you have — product and volume if you know them. Patients who arrive describing a puffy blue under-eye from treatment elsewhere are among the more common corrections we see, and it resolves.