A tear trough filler is an injectable treatment that’s used under the eyes. Tear trough fillers are an effective way to treat dark circles under the eyes and under-eye hollows. By injecting filler under the eyes, we fill the volume lost by ageing – lightening dark circles, filling under eye hollows and wrinkles. The product most often used in this area is one typically made of hyaluronic acid, although other ingredients may be used.