Vol 11-R2- Eyelid

SRPS • Volume 11 • Issue R2 • 2010
eyelids have been identified:
1. single eyelid: no lid crease with puffiness
2. low eyelid crease: low-seated, nasally
tapered, inside-fold type of crease
3. double eyelid: lid crease parallel to
the lid margin 6
Jeong et al. 7 found that there are three
reasons for the absent or lower crease in the Asian
upper eyelid:
1. The orbital septum fuses to the levator
aponeurosis at variable distances below
the superior tarsal border.
2. Preaponeurotic fat pad protrusion and
a thick subcutaneous fat layer prevent
levator fibers from extending toward the
skin near the superior tarsal border.
3. The primary insertion of the levator
aponeurosis into the orbicularis muscle
and into the upper eyelid skin occurs
closer to the eyelid margin in Asians.
The lower eyelid crease is formed by the fascial
extensions of the capsulopalpebral fascia, which also
pass through the orbicularis oculi muscle and insert
onto the skin. 8 Lim et al. 9 reported that in Asians,
these fascial extensions do not extend to the skin;
therefore, a palpebral crease is not found. Kakizaki
et al. 10 stated that the reason for the indistinct
lower lid crease in Asians is the higher or indistinct
septum fusion, the anterior and superior orbital
fat projection, and the overriding of the preseptal
orbicularis muscle.
Eyelid Margin and Lacrimal Pump
The eyelid margin has several significant structures.
Both the upper and lower eyelid margins have a
punctum medially. The punctum opens into the
canaliculus of the lacrimal system. Tears drain via
the canaliculi and into the nasolacrimal sac and
then to the lacrimal duct by both an active and a
passive mechanism. The lacrimal pump actively
sucks tears into the lacrimal sac with each blink.
The contraction of the orbicularis muscle brings
the lower punctum medially, closes the ampulla,
and displaces the lateral wall of the lacrimal sac
laterally, creating a negative pressure in the sac. This
2
draws the tears from the common canaliculus into
the sac. 11,12 The loss of the active component of tear
drainage is partially responsible for epiphora in
cases of facial nerve palsy. Malpositions of the lower
eyelid and the puncti can also lead to epiphora.
Along the length of the eyelid margin is the
gray line, corresponding histologically to the most
superficial portion of the orbicularis muscle, the
muscle of Riolan, and to the avascular plane of the
lid. 2 Anterior to the gray line, the eyelashes or cilia
arise. Posterior to the gray line are the orifices to the
meibomian glands. Meibomian glands are modified
holocrine sebaceous glands that produce lipid
secretions. Oil from the openings forms a reservoir
on the skin of the lid margin and is supplied to the
tear film with each blink. 2 Other glands found on
the skin of the eyelids are the sweat eccrine glands
of Zeis and holocrine glands of Moll.
Orbicularis Oculi Muscle
The orbicularis muscle is arranged in concentric
bands and is the main protractor of the eyelid. It
can be separated into orbital and palpebral portions.
It is innervated by cranial nerve VII. Its antagonist,
the levator, is innervated by cranial nerve III. The
orbital portion is involved in forced eyelid closure.
The palpebral portion can be divided into pretarsal
and preseptal parts (Fig. 2). 13 The palpebral portions
are involved in involuntary lid movements, such as
blinking. 13
The pretarsal orbicularis attaches medially
to the anterior and posterior arms of the medial
canthal ligament to surround the lacrimal sac,
and the superior and inferior lacrimal canaliculi
are found within its muscle fibers. It plays a vital
part in the lacrimal pump mechanism. Laterally,
the pretarsal orbicularis joins the lateral canthal
ligament at the Whitnall tubercle. The preseptal and
orbital components attach medially to the medial
canthal ligament and laterally to the zygoma, lateral
to the orbital rim. In addition to the formerly
mentioned attachments, the orbital orbicularis
attaches medially to the maxillary and frontal bones
and extends peripherally to overlie the orbital rims.
A small segment of the orbicularis oculi muscle,