The levator aponeurosis transmits levator palpebrae superioris muscle force to the eyelid. Thus, any disruption in its anatomy or function can lead to ptosis.
Eyelids with aponeurotic defects characteristically have a high or an absent upper eyelid crease secondary to upward displacement or loss of the insertion of levator fibers into the skin. Thinning of the eyelid superior to the upper tarsal plate is often an associated finding. Because the levator muscle itself is healthy, levator function in aponeurotic ptosis is usually normal (15 mm). Acquired aponeurotic ptosis may worsen in downgaze, thus interfering with the patient’s ability to read, as well as limiting the superior visual field. Table 12-1 compares acquired aponeurotic ptosis with congenital myogenic ptosis.
Congenital neurogenic ptosis is caused by innervational defects that occur during embryonic development. This condition is relatively rare and is most commonly associated with congenital cranial nerve III (CN III) palsy, congenital Horner syndrome, or Marcus Gunn jaw-winking syndrome.
Congenital oculomotor nerve (CN III) palsy is manifested as ptosis together with inability to elevate, depress, or adduct the globe. The pupils may also be dilated. This palsy may be partial or complete, but ptosis is very rarely an isolated finding. It is uncommon to find aberrant innervation in congenital CN III palsies. Management of strabismus and amblyopia is difficult in many cases of congenital CN III palsy. Treatment of the associated ptosis is also complicated, usually requiring a frontalis suspension procedure, which often leads to some degree of lagophthalmos. As a result of lagophthalmos, poor ocular motility, and poor postoperative eyelid excursion, postoperative management may be complicated by diplopia, exposure keratopathy, and corneal ulceration.
Congenital Horner syndrome is a manifestation of an interruption in the sympathetic nerve chain. It can cause mild ptosis associated with miosis, anhidrosis, and decreased pigmentation of the iris on the involved side. The mild ptosis of Horner syndrome results from an innervational deficit to the Müller muscle. Decreased sympathetic tone to the inferior tarsal muscle in the lower eyelid results in elevation of the lower eyelid, sometimes referred to as reverse ptosis. The combination of upper ptosis and lower eyelid elevation decreases the vertical palpebral fissure and may falsely suggest enophthalmos. The pupillary miosis is most apparent in dim illumination, when the contralateral pupil dilates more.
Congenital neurogenic ptosis may also be synkinetic. Marcus Gunn jaw-winking syndrome is the most common form of congenital synkinetic neurogenic ptosis (Video 12-4, Fig 12-15). In this synkinetic syndrome, the unilaterally ptotic eyelid elevates with jaw movements. The movement that most commonly causes elevation of the ptotic eyelid is lateral mandibular movement to the contralateral side. This phenomenon is usually first noticed by the mother when she is feeding or nursing the baby. This synkinesis is thought to be caused by aberrant connections between the motor division of CN V and the levator muscle. Infrequently, this syndrome is associated with abnormal connections between CN III and other cranial nerves. Some forms of Duane retraction syndrome also cause elevation of a ptotic eyelid with movement of the globe. This congenital syndrome is also thought to result from aberrant nerve connections.
Marcus Gunn jaw-winking. Courtesy of Pete Setabutr, MD.
Acquired neurogenic ptosis results from interruption of normally developed innervation and is most often secondary to an acquired CN III palsy, Horner syndrome, or MG.
Figure 12-15 Marcus Gunn jaw-winking ptosis (synkinesis linking cranial nerve V to cranial nerve III). A, Relaxed position with ptosis of the left upper eyelid. B, When the mandible is moved to the left, the eyelid position remains low. C, Moving the mandible to the right elevates the left upper eyelid.
(Courtesy of Jill Foster, MD.)
Delineation of the cause of acquired CN III (oculomotor) palsy is important. Distinction must be made between ischemic and compressive etiologies. Most acquired CN III palsies are ischemic and associated with diabetes mellitus, hypertension, or arteriosclerotic disease. Typically, ischemic acquired CN III palsies do not include pupillary abnormalities, they may be associated with pain, and they resolve spontaneously with satisfactory levator function within 3 months. If a pupil-sparing CN III palsy fails to resolve spontaneously within 3–6 months, further workup for a compressive lesion is indicated. However, if a patient presents with a CN III palsy involving the pupil, an immediate workup (including neuroimaging) should commence in order to rule out a compressive neoplastic or aneurysmal lesion. Surgical correction of ptosis related to CN III palsy usually requires frontalis suspension and should be reserved for patients in whom strabismus surgery allows single binocular vision in a useful field of gaze.
Temporary neurogenic ptosis can be caused by inadvertent diffusion of botulinum toxin into the levator muscle complex following therapeutic injection in the forehead or orbital region. The resultant ptosis usually resolves after several weeks.
MG is an autoimmune disorder in which autoantibodies attack the acetylcholine receptors of the neuromuscular junction. The disease is most often generalized and systemic. Approximately 10% of patients with generalized MG have an associated thymoma; thus, chest computed tomography (CT) should be considered for all patients with MG to rule out this lesion. Surgical thymectomy results in clinical improvement in 75% of cases of generalized MG and complete remission in 35% of cases. Early manifestations of MG are often ophthalmic, with ptosis being the most common presenting sign; diplopia is often present as well. When the effects of MG are isolated to the periocular musculature, the condition is called ocular myasthenia gravis. Marked variability in the degree of ptosis during the day and complaints of diplopia should suggest ocular MG. Other autoimmune disorders may occur in myasthenic patients.
No single test for MG will detect all cases. Neuro-ophthalmologic consultation is useful in the evaluation and treatment of MG. Surgical treatment of ptosis should be delayed until medical management of MG is maximized. Because of the variability of levator function, frontalis suspension may be considered. See BCSC Section 5, Neuro-Ophthalmology, for further discussion.
In mechanical ptosis, the upper eyelid is weighed down by a mass or swelling in the eyelid or orbit. It may be caused by a congenital abnormality, such as a plexiform neurofibroma or hemangioma, or by an acquired neoplasm, such as a large chalazion (Fig 12-16) or skin carcinoma. Postsurgical or posttraumatic edema may also cause temporary mechanical ptosis.
Trauma to the levator aponeurosis or the levator palpebrae superioris muscle may also cause ptosis through myogenic, aponeurotic, neurogenic, or mechanical defects. An eyelid laceration that exposes preaponeurotic fat indicates that the orbital septum has been violated and suggests possible damage to the levator muscle and/or aponeurosis. Exploration of the levator and repair may be indicated in this situation. Orbital and neurosurgical procedures can also lead to traumatic ptosis. Since such ptosis may resolve or improve spontaneously, the ophthalmologist typically observes the patient for an extended period before considering surgical intervention.
Pseudoptosis, which gives the appearance of a drooping eyelid, should be differentiated from true ptosis. An eyelid may appear to be abnormally low in various conditions, including brow ptosis, hypertropia, enophthalmos, microphthalmia, anophthalmia, phthisis bulbi, or a superior sulcus defect secondary to trauma or other causes. Contralateral upper eyelid retraction may also simulate ptosis. The term pseudoptosis is also sometimes used to describe dermatochalasis, the condition in which excess upper eyelid skin overhangs the eyelid margin (Fig 12-17).
Figure 12-16 Mechanical ptosis. A, Chalazion of the left upper eyelid causing mechanical ptosis. B, Ptosis is improved after incision and drainage of the chalazion.
(Courtesy of Bobby S. Korn, MD, PhD.)
Figure 12-17 Bilateral upper dermatochalasis. A, Patient with dermatochalasis and pseudoptosis of both upper eyelids. B, Clearance of the visual axis is achieved through blepharoplasty alone.
(Courtesy of Bobby S. Korn, MD, PhD.)
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.