Introduction

In youth, the transition between the lower eyelid and cheek is imperceptible and smooth. The eyes are balanced and in harmony with the surrounding tissue and the face as a whole with gentle sloping contours most often without distinct demarcations. Skin texture is consistent and smooth, while the surface is unblemished and uniform in color. Over the years, every aspect of youthful countenance changes through a cascade of events known simply as the aging process.

The infraorbital hollow (IOH) refers to the curvilinear or U-shaped depression under the eyes from the nasal bone to the outer corner of the eye and comprises three core elements: the ‘tear trough’ and nasojugal fold medially, and the palpebromalar groove laterally (Fig. 16.1). Although the terms ‘tear trough’ and ‘nasojugal fold’ have historically been used interchangeably, the former – which occurs mildly in all people across all ages – refers to the superior aspect of the latter. A sign of early aging, the deepening of the tear trough leads to a true indentation at the junction of the thin eyelid skin above and thicker skin of the cheek below. Later, the mid-cheek may descend, accentuating a flat or hollow crescent below the eye. The appearance of hollows and dark circles under the eye is the interplay of various factors. Genetics and habits / environmental exposures lead to dyschromias and pigmentation; soft tissue laxity, subcutaneous volume alterations, changes in bony landmarks, and redistribution of superficial fat all lead to shadowed contours and deepening folds. Periorbital volumetric shifting and loss is not an isolated event but part of a global shift in the contours of the aging face.

Figure 16.1 Anatomy of the infraorbital hollow.

There is little to no superficial fat under the lower eyelid. The orbicularis oculi muscle has direct bony attachment for approximately one-third of the orbital rim length, from the nasal bone to the medial limbus. Laterally, orbicularis-retaining ligaments connect the deep surface of the skin to bone. Retaining ligaments weaken, facial bones recede, and volume decreases in the deep fat pads, causing the cheek to descend and superficial fat to accumulate under the eye, all of which combine with genetically predisposed discolorations and bony changes to produce the perception of hollowed and sometimes baggy eyes, deep and shadowed tear troughs, and an aged, fatigued appearance refractory to cosmetic attempts at concealment (Fig. 16.1).

Treatment of the periorbital area with injectable agents allows little room for error and requires careful patient selection, careful choice of filling agent, and precise technique to avoid complications and ensure optimal outcome.

Candidates for augmentation of the infraorbital hollow

Proper patient selection is critical and relies on careful ophthalmologic and medical history and physical assessment. Poor candidates are unlikely to obtain optimal results and may not be satisfied with results and are at higher risk of side effects, such as visibility and irregularity (Table 16.1). Patients with diseases or metabolic conditions that predispose to lower eyelid irregularity or bleeding and infection should be excluded, and all manner of anticoagulant medications and supplements discontinued if medically safe for at least 2 weeks prior to treatment. Some patients have genetically determined pigmentation that may look like a tear trough but without an indentation that can be filled. Pigmented dark lower eyelid circles cannot be improved by fillers and can, in fact, be worsened by treatment. Older patients with thinner, crepe-like, inelastic skin and individuals with pre-existing malar edema – whether metabolic (thyroid disease) or otherwise (i.e. chronic sinus disease, prior surgery, etc.) – may not respond well and also have an increased risk for adverse events and dissatisfaction with these treatments. Patients with orbital fat herniation and significant skin laxity would benefit first from lower lid blepharoplasty or other surgical procedures. Injection works best in patients with thicker and smooth skin and a well-defined tear trough or defined maxillary retrusion / hypoplasia (common in young Asian females), without excessively protruding eyelid fat or excess eyelid skin.

Table 16.1 Identifying candidates for augmentation of the infraorbital hollow

Best candidates	Poor candidates
Young patients with good skin elasticity	Elderly patients with poor skin elasticity
Thick smooth skin	Very thin skin
Good skin tone	Transparent or dyspigmented skin
Minimal laxity	Significant skin laxity
Mild-to-moderate tear troughs	Extremely deep tear troughs