tum fuses with the capsulopalpebral fascia 5 mm inferior to the lower
border of the tarsus.
14
In addition, in many Asians a subcutaneous
fat pad exists anterior to the septum.
18
The strength of the orbital septum varies among individuals and
with age. With time, the septum attenuates, resulting in anterior pro-
lapse of orbital fat.
8,19
The tarsal plates (Fig. 1-2) provide rigidity to the eyelids. They
are composed of dense, fibrous connective tissue. The upper tarsus
measures 10–12 mm vertically, and the lower measures 3–5 mm.
20
The tarsal borders adjacent to the lid margin are straight, whereas
the opposite edges have a convex curvature. The posterior edge of the
tarsus is firmly attached to the palpebral conjunctiva, which extends
onto the eyelid margin and terminates at the gray line.
Within the tarsus lie branched, acinar, sebaceous glands with long
central ducts. Known as the meibomian glands, they open at the eye-
lid margin just posterior to the gray line and secrete the oily layer of
the tear film. There are about 25 in the upper eyelid and 20 in the
lower.
11
Inflammation of these glands, known as meibomitis, may,
over a long term, result in distichiasis,
21
or abnormal hair follicles
that, unlike the normal eyelashes, curve inward toward the globe,
causing discomfort and possibly corneal abrasion. A common treat-
ment for distichiasis, electrohyfrecation, may cause focal necrosis of
the tarsus, resulting in notching at the eyelid margin.
8
Similarly, ex-
cessive cryotherapy for distichiasis can cause a wider-than-planned
area of lash loss and scarring.
Emanating from the medial and lateral borders of the tarsi and
anchoring them to the orbital rim are the canthal ligaments. They
are formed by a confluence of the upper and lower crura, the exten-
sions of the margins of the upper and lower tarsi, respectively. They
support not only the tarsi but also the orbicularis. The medial can-
thal ligament splits into three arms: anterior, posterior, and supe-
rior. The anterior arm attaches to the maxillary bone, anterior to the
lacrimal crest; the posterior arm attaches to the posterior lacrimal
crest
22,23
; and the superior arm inserts onto the orbital process of the
frontal bone.
24
The lateral canthal ligament inserts 3–4 mm inside
the lateral orbital rim at Whitnall’s tubercle, on the zygomatic bone.
25, 26
During lower eyelid-tightening procedures, which usually involve sur-
gical manipulation of the lateral aspect of the lower tarsus and the
lateral canthal ligament, the posterior direction and periosteal in-
sertion of the lateral canthal ligament must be reestablished. Laxity
of the canthal ligaments can cause ectropion, as well as cosmetically
apparent shortening of the horizontal palpebral fissure.
27
6 Cosmetic Facial Anatomy