Upper Lid Retractor: Levator

The primary retractor of the upper eyelid is the levator muscle. The levator originates on the orbital roof near the apex, in front of the optic foramen and anterior to the superior rectus muscle. The levator muscle portion is 40 mm long, and the levator aponeurosis is 14–20 mm length.

Whitnall’s ligament or superior traverse ligament is a condensation of elastic fibers of the anterior sheath of the levator muscle. It is located between the transition of the levator aponeurosis and muscle. It provides the suspension support for the upper eyelid and superior orbital tissues. It is thought to transfer the vector of force of the levator muscle from anterior–posterior to superior–inferior. It is analogous to Lockwood’s ligament in the lower eyelid. Medially it attaches near the trochlea and superior oblique tendon, and laterally, it runs through the lacrimal gland, and attaches to the inside of the lateral orbital wall, approximately 10 mm above the lateral tubercle.1–4

The levator aponeurosis divides into an anterior and posterior portion just above the superior tarsal border. The anterior portion inserts into the pretarsal orbicularis. The most superior portion of these attachments forms the eyelid crease with contraction of the levator complex (Fig. 2.2). The posterior portion inserts onto the anterior surface of the tarsus. The aponeurosis appears as a thick whitish band between Whitnall’s ligament and the tarsal plate (Fig. 2.3).

The medial horn of levator aponeurosis inserts onto the posterior lacrimal crest.

The lateral horn divides the orbital and palpebral lobes of the lacrimal gland, then inserts onto the lateral orbital tubercle. The lateral horn is much stronger than the medial horn and this is thought to account for temporal flare in thyroid eye disease.

Upper Lid Retractor: Müller’s Muscle

Müller’s muscle originates underneath the levator aponeurosis, 12–13 mm above the upper tarsal margin. It is 15–20 mm wide. It is sympathetically innervated, extends inferiorly to insert at the superior tarsal border, and provides 2 mm of elevation. If interrupted, as in Horner’s syndrome, it causes a mild ptosis. Müller’s muscle is firmly attached to the palpebral conjunctiva. The peripheral arterial arcade is located between the levator aponeurosis and Müller’s muscle above the superior tarsal border and can serve as a useful surgical landmark.1–4

Upper Lid Retractor: Frontalis

The frontalis muscle acts to lift the eyebrows and is considered a weak retractor of the upper lids. Elevation of the brow can cause 2 mm of elevation of the upper eyelid. Contraction of the frontalis muscle causes horizontal furrows in the forehead. The absence of frontalis over the tail end of the brow accounts for brow hooding, often seen with age. The frontal nerve, the superior branch of the facial nerve, innervates the frontalis.

Lower Lid Retractors

The lower eyelid retractors serve to depress the eyelid in downgaze, and maintain the upright position of the tarsal plate. The capsulopalpebral fascia in the lower lid is analogous to the levator in the upper lid (Fig. 2.4). It is fibrous tissue that originates from the sheath of the inferior rectus muscle, divides as it encircles the inferior oblique and fuses with the sheath of the inferior oblique. Then the two portions join to form Lockwood’s ligament.

The inferior tarsal muscle, also known as the inferior palpebral muscle, is analogous to Müllers muscle in the upper eyelid. It runs between the capsulopalpebral fascia and conjunctiva. It starts at Lockwood’s ligament and extends to the inferior conjunctival fornix with insertion onto the inferior tarsal border, where it fuses with the orbital septum. It is also sympathetically innervated. Sympathetic disruption, as in Horner’s syndrome, accounts for ‘inverse or reverse ptosis’ of the lower eyelid. The lower lid retractors are not easily separated and are often collectively referred to as the lower lid retractors.