Vol 11-R2- Eyelid

SRPS • Volume 11 • Issue R2 • 2010
called the muscle of Riolan, is separated from the
pretarsal component by the eyelash follicles and
forms the gray line along the eyelid margins. 14,15
Muzaffar et al. 16 reported that the orbicularisretaining
ligament is a bilaminar septum-like
structure attaching the orbicularis oculi to the
inferior orbital rim. The attachment is weakest
centrally and tightest over the inferolateral
orbital rim.
Ghavami et al. 17 further clarified that the
orbicularis-retaining ligament is a circumferential,
periorbital structure and that the orbicularis
retaining ligament of the superior orbit arises 2 to 3
mm above the orbital rim in the mid orbit.
Anterior and Posterior Lamellae
The eyelid is divided into two lamellae (Fig. 3). 13
The anterior lamella consists of skin and the
orbicularis oculi muscle, and the posterior lamella
consists of the tarsal plate and conjunctiva. 15
Tarsus
The tarsal plates act as the skeleton of the eyelids,
providing semirigid support. 18 The tarsus is
composed of dense regular connective tissue and
contains the Meibomian glands. 4 The superior tarsus
is 10 to 12 mm at its greatest vertical dimension,
and the inferior tarsus is 3 to 5 mm. 18 The upper
and lower tarsal plates are similar in length (29 mm)
and thickness (1 mm). 2 The Meibomian glands
are modified holocrine sebaceous glands and are
oriented vertically in parallel rows through the
tarsus. The upper lid contains 25 meibomian glands,
and the lower lid contains 20. 13
Conjunctiva
The palpebral conjunctiva lines the inner surface
of the eyelids and is covered by a non-keratinized
epithelium. Holocrine glands known as goblet
cells secrete mucous and are located throughout
the conjunctiva. The goblet cells are mainly
concentrated in the conjunctival fornices and at the
caruncle. The palpebral conjunctiva is continuous
with the conjunctival fornices and merges with
the bulbar conjunctiva overlying the globe. The
4
conjunctiva becomes freely mobile in the fornices.
The bulbar conjunctiva lines the sclera and
terminates at the limbus.
Orbital Septum
The orbital septum lies beneath the orbicularis
muscle and consists of a thin sheet of connective
tissue. It encircles the orbit as an extension of the
periosteum of the roof and the floor of the orbit. 2
The orbital septum acts as a barrier of the orbital
contents, and the orbital fat can be found posterior
to it. It extends from the arcus marginalis, where
the periosteum and periorbita fuse, toward the
tarsus. 3 In the upper eyelid the septum inserts at the
levator, approximately 2 to 3 mm above the superior
edge of the tarsus. In the lower eyelid, the septum
inserts to the inferior edge of the tarsus. 19 The
septum attaches medially to the lower end of the
anterior lacrimal crest, called the lacrimal tubercle. It
continues from the lower to upper eyelid by passing
under the medial orbicularis muscle. 3 Putterman 19
noted that the septum is difficult to trace laterally
because it blends with the lateral canthal tendon
and the lateral horn of the levator. The septum also
takes the shape of an arch under the supraorbital
notch and around the supratrochlear and
infratrochlear nerves and vessels. Weakness in the
orbital septum contributes to herniation of the
orbital fat.
Reid et al. 20 described a distinct fibrous
anatomic layer, which extends from the orbital
septum to cover the tarsus. They named the fibrous
structure the septal extension. They described the
preaponeurotic fat layer covered by the septal
extension, which extends to cover the tarsus along
its anterior border to the ciliary margin. The septal
extension was found between the orbicularis
oculi and the levator aponeurosis, distinct from
the levator tissue. Fibrous connections extending
from the levator aponeurosis penetrate the septal
extension and the orbicularis muscle, connecting the
levator-dermal link to the septal extension. Tension
placed on the orbital septum leads to referred
tension on the septal extension and secondary
lagophthalmos. The authors stated that the findings