1. What Tear Trough Filler Is, and the One Problem It Actually Solves
Tear trough filler, usually called under eye filler, places a small amount of hyaluronic acid gel into the groove that runs from the inner corner of the eye outward along the bony orbital rim. The aim is to soften the shadow that groove casts, so the lower lid transitions smoothly into the cheek rather than dropping into a trench. It works on one specific finding: a genuine hollow, where volume has been lost along the rim or was never there. When the hollow is the problem, filling it well is a striking change, visible the same day.
What it does not do is brighten a tired looking under eye in general. Pigment, thin skin, protruding fat and loose skin all produce the same complaint in the mirror, and none improves because material was added along the bone. Being told plainly which one you have is the most valuable thing a consultation produces.
Two anatomical facts explain most of what follows. The skin of the lower lid is the thinnest on the body, so anything beneath it can show through, and the tissue underneath drains poorly and tolerates extra material badly.