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Page 2 of 10 Somenek. Plast Aesthet Res 2022;9:16 https://dx.doi.org/10.20517/2347-9264.2021.84

ANATOMY AND PHYSIOLOGY OF THE EYELIDS
An intimate comprehension of anatomy is the main component of any successful operation. Eyelids have
complex anatomy, comprising an array of skin, muscles, blood vessels, and nerves. In addition, the mobile
nature of the eyelids along with their importance of the air-tear interface can create challenges for the
reconstructive surgeon.

The normal eye has an elliptical shape with the lateral canthus positioned approximately 2 mm higher than
the medial canthus. Senescence can cause inferior dystopia of the lateral canthus, in contrast to the medial
canthus, which tends to have a more stable position throughout adulthood. The palpebral fissure is defined
as the aperture between the upper and lower eyelids. The horizontal palpebral fissure measures 28-30 mm,
while vertically, it measures around 8-12 mm.

For the purposes of reconstruction, the eyelid was broken down into two distinct anatomical lamellae. The
anterior lamella contains skin and the orbicularis oculi, while the posterior lamella is comprised of the tarsal
plate and the conjunctiva. A gray line is visible along both eyelid margins, which marks the junction of the
two lamellae. Posterior to the gray line is the mucocutaneous junction at the meibomian gland openings.
The lower eyelid has similar structures, except the retractor is the capsulopalpebral fascia, which is an
extension of the inferior rectus muscle [Figure 1].

The protractor of the eyelid is the orbicularis oculi muscle which is concentrically arranged around the
palpebral fissure and divided into three segments. The pretarsal segment lies over the region of the tarsal
plate and is responsible for involuntary blinking. Lastly, the orbital fibers are the outermost extension of the
muscle and overlie the orbital rim, interdigitating with the frontalis muscle superiorly and the superficial
aponeurotic system inferiorly.

The lateral canthal tendon functions as an anchor of the tarsal plates posteriorly and superolaterally to
Whitnall’s tubercle. This ensures that the lateral eyelids abut the globe in all positions of gaze. The medial
canthal tendon supports the lacrimal canaliculi and blends with the lacrimal sac fascia. The deep
attachments of both canthal tendons need to be recreated in order to prevent malpositions of the eyelids.

Periorbital skin is the thinnest on the body and contains lower numbers of sebaceous glands than other
areas. These glands produce sebum which lubricates and waterproofs the skin. Since there are fewer glands
present, periorbital skin can tend to dry out and wrinkle faster. A lack of subcutaneous tissues beneath the
thin eyelid skin means the skin tightly adheres to the underlying muscles, which are constantly contracting
and transmitting movement to the delicate tissue.

Tear production and flow are essential components of orbital physiology. Tears are composed of three
layers: an outer lipid layer, a middle aqueous layer, and an inner mucin layer. Tear drainage occurs via the
lacrimal outflow system in each medial canthus. Epiphora, or excessive tearing, can be a problem after
eyelid reconstruction due to an imbalance in the production and outflow systems. This can be caused by a
reflex overproduction in response to a corneal irritation from a resulting eyelid malposition from the
reconstruction. Damage to the lacrimal outflow system can cause an interruption in the tear drainage
system.

Indications of eyelid reconstruction
Evaluation of eyelid defect
A preoperative analysis is essential to assess the possible areas for reconstruction to minimize surgical