Clinical Comment: Ectropion and

Entropion

Eversion of the eyelid margin is called ectropion (Figure 9-6), the common cause of which is loss of muscle tone, a normal occurrence in the aging process. As the lid margin falls away from its position against the globe, the lacrimal punctum

is no longer in position to drain the tears from the lacrimal lake. Epiphora, an overflow of tears onto the cheek, may occur, causing maceration of the delicate skin in this area.

Inversion of the lid margin is called entropion and may result from spasm of the orbicularis oculi muscle causing the lid margin to turn inward (Figure 9-7). This inward turning puts the eyelashes in contact with the globe and, unless relieved, can cause corneal abrasion. Scarring of the lid after trauma or disease may also cause entropion. Both ectropion and entropion are more common in the lower lid and can be corrected surgically, if necessary. The anatomic relationship­

of the muscular and connective tissue components is an important consideration when repair is done.20-22

Orbital Portion

The orbital portion of the orbicularis oculi muscle is attached superiorly to the orbital margin, medial to the supraorbital notch. The fibers encircle the area outer to the palpebral portion and attach inferiorly to the orbital margin, medial to the infraorbital foramen.2 These concentric circular fibers extend throughout the rest of the lid and over the orbital rim.

Orbicularis Action

The orbicularis oculi muscle is innervated by cranial nerve VII (the facial nerve). Contraction of the palpebral portion closes the eyelid gently, and the palpebral orbicularis is the muscle of action in an involuntary blink and a voluntary wink; relaxation of the levator

muscle follows.23 Spontaneous involuntary blinking renews the precorneal tear film. A reflex blink is protective and may be elicited by a number of stimuli—a loud noise; corneal, conjunctival, or cilial touch; or the sudden approach of an object. When the orbital portion of the orbicularis contracts, the eye is closed tightly, and the areas surrounding the lids—the forehead, temple, and cheek—are involved in the contraction. Such eyelid closure is often a protective mechanism against ocular pain or after injury, and is called reflex blepharospasm. If the lids are closed tightly in a strong contraction, forces compressing the orbital contents can significantly increase the intraocular pressure.24

The antagonist to the palpebral portion of the orbicularis is the levator muscle. The antagonist to the orbital portion is the frontalis muscle.

Superior Palpebral Levator Muscle

The superior palpebral levator muscle, the retractor of the upper eyelid, is located within the orbit above the globe and extends into the upper lid. It originates on the lesser wing of the sphenoid bone above and in front of the optic foramen, and its sheath blends with the sheath of the superior rectus muscle. As the levator approaches the eyelid from its posterior origin at the orbital apex, a ligament, the superior transverse ligament (Whitnall’s ligament) may act as a fulcrum, changing the anteroposterior direction of the levator to superoinferior10,12,25-28 (Figure 9-8). The superior transverse ligament is a fibrous band that spans the anterior superior orbit from the trochlea to the lacrimal gland fascia. It provides support for the upper lid and orbital structures as well as acting as a fulcrum. The ligament is located at the point where the levator muscle fibers end and the aponeurosis begins.29

Severe involutional (senile) ectropion. (From Kanski JJ: Clinical ophthalmology: a systematic approach, ed 5, Oxford, UK, 2003, Butterworth-Heinemann.)

Involutional (senile) entropion. (From Kanski JJ: Clinical ophthalmology:­ a systematic approach, ed 5, Oxford, UK, 2003, Butterworth-Heinemann.)