Surgical anatomy of the lower eyelid relating to lower blepharoplasty

The aim of this review is to familiarize the reader with the critical lower eyelid anatomy as is related to lower blepharoplasty or a midface lift. The contents include 1) the lacrimal canaliculus in the lower eyelid: the depth and width (diameter) of the vertical portion were $2.58{\pm}0.24$ mm and $0.44{\pm}0.07$ mm, respectively. A vertical portion of the canaliculus was about 1 mm ($1.11{\pm}0.16$ mm) deep, and the horizontal portion was about 2~3 mm ($2.08{\pm}2.74$ mm) long 2 mm below the mucocutaneous junction, which is where an incision may be made when performing epicanthoplasty. 2) Motor innervation to the lower orbiculis oculi muscle: the pretarsal and preseptal OOMs were innervated by fi ve to seven terminal twigs of the zygomatic branches of the facial nerve that approached the muscle at a right angle. The mean horizontal distance between the lateral canthus and the zygomatic branch was $2.31{\pm}0.29$ cm (range: 1.7~2.7 cm) and the vertical distance was $1.20{\pm}0.20$ cm (range: 0.8~1.5 cm). 3) Sensory innervation of the lower eyelid skin: the majority of the terminal branches (93.8%) of the ION were distributed to the medial to the lateral canthus. Most (99.4%) of the terminal branches of the ZFN were distributed to lateral to the lateral canthus. 4) Retractor of the lower eyelid; capsulopalpebral fascia (CPF): the orbital septum blended with the CPF most closely at 3.7~5.4 mm beneath the lower tarsal border and differently at $3.7{\pm}0.7$ mm on the medial limbus line, $4.3{\pm}0.8$ mm on the midpupillary line and $5.4{\pm}1.0$ mm on the lateral limbus line. 5) Arcuate expansion (AE): The AE was a fibrous band expanding from the inferolateral orbital rim to the medial canthal ligament. A sector (fan-shaped) of the AE originated in the angle of 5 to 80 degrees at the circumference of the inferolateral orbital rim circle, falling within the range of 3 to 5.5 o'clock, and then it tapered and attached to the inferior border of the medial canthal ligament. 6) Suborbicularis oculi fat (SOOF) in the lower eyelid: the SOOF was located in the inferolateral side of the orbit within a range between medial +15 and lateral -89 degrees to a vertical midpupillary line. Histologically, the SOOF was situated deep to the Orbicularis oculi muscle and superficial to the orbital septum and periosteum. Th e SOOF consisted more of fibrofatty tissue rather than being the pure fatty nature like orbital fat. I hope surgeons can achieve desirable outcomes with the knowledge reviewed in this article.