Vol 11-R2- Eyelid

SRPS • Volume 11 • Issue R2 • 2010
functions to convert the anterior-posterior pulling
force of the levator to a superior-inferior direction,
which raises and lowers the eyelid. 21−23 The levator
aponeurosis joins the orbital septum above the
superior border of the tarsus and sends fibrous
strands between the orbicularis oculi muscle septa
to the skin to make the lid crease. 22 The normal
excursion of the levator muscle is 15 mm. 3
Müller muscle is a smooth, sympathetically
innervated muscle in the upper eyelid. It originates
from the undersurface of the levator muscle 8 to 10
mm above the superior tarsal border and attaches
to the superior edge of the tarsus. 22 It functions to
provide 2 mm of lid retraction, and its interruption
in Horner syndrome causes mild ptosis. 24
Kakizaki et al. 25 found that the levator
aponeurosis has doubly stratified layers that include
smooth muscle. The authors suggested that the
levator aponeurosis regulates tension in the anterior
lamella of the upper eyelid as the Müller muscle
regulates the tension of the posterior lamella of
the upper eyelid. 26 The structures lead to ordered
movement in the upper eyelid.
Lower Eyelid Retractors
In the lower eyelid, the retractors originate from
the capsulopalpebral head of the inferior rectus
muscle. The capsulopalpebral fascia is analogous to
the levator in the lower eyelid. The capsulopalpebral
head splits around the inferior oblique muscle
and fuses again to form Lockwood ligament
(similar to Whitnall ligament in the upper lid).
The inferior tarsal muscle is a sympathetically
innervated muscle analogous to Müller muscle of
the upper lid. It originates on the posterior surface
of capsulopalpebral fascia. The inferior tarsal muscle,
capsulopalpebral fascia, and orbital septum insert at
a fusion point into the anterior and inferior surface
and base of the tarsus. 22 The capsulopalpebral
fascia sends anterior projections that penetrate
through the orbicularis to the skin to create a
transverse crease. 3
Preaponeurotic Fat
The preaponeurotic fat serves as an important
6
structure in eyelid anatomy. It is a crucial surgical
landmark. The levator aponeurosis lies just posterior
to the preaponeurotic fat, and the septum lies
just anteriorly. In the upper eyelid, two fat pads
are found: the nasal and middle fat pads (Fig. 5).
The nasal fat pad lies beneath the trochlea. The
lower eyelid has three fat pads. The nasal fat pad is
separated posteriorly from the central fat pad by the
inferior oblique muscle. The central and lateral fat
pads are connected in deeper layers but anteriorly
are divided into two pads by a dense septal
partition. 22 The nasal fat pads are distinctly whiter
in color in both the upper and lower eyelids when
compared with the yellow color of the more lateral
fat pads.
Medial Canthus
The medial canthus provides a support point for the
eyelids, helps provide its normal angular shape, and
assists the lacrimal pump apparatus. 27 It is rigidly
fixed to the orbital wall.
McCord et al. 22 illustrated the structure of
the medial canthus and reported that medially, the
pretarsal orbicularis produces two heads that pass
superficial and deep to the canaliculi. The anterior,
more superficial, pretarsal orbicularis muscle forms
the anterior crus of the medial canthal tendon that
inserts into the frontal process of the maxillary
bone. The posterior, deeper, pretarsal orbicularis
inserts into the posterior lacrimal crest. The muscle
is known as Horner muscle. The deep pretarsal
orbicularis inserts on the posterior lacrimal crest
and the lacrimal fascia. The deep preseptal fibers
insert mainly on the lacrimal fascia, and this is
known as Jones muscle. The preseptal muscle forms
the horizontal raphe laterally, and medially, it inserts
into the anterior crus of the medial canthal tendon.
Lateral Canthus
The lateral canthal tendon resembles the medial
canthal tendon in that it supports the lids by
supplying a tendinous attachment of pretarsal
orbicularis oculi muscle and ligamentous
attachment of the tarsal plates to the periosteum
of the lateral orbital tubercle. It also allows