Ptosis

Harsha S. Reddy

Di Coneybeare

THE CLINICAL CHALLENGE

Eyelid droop, called blepharoptosis, is often abbreviated to simply ptosis. Ptosis is defined as the inferior displacement of upper eyelid margin from its anatomic position, normally, about 1 to 2 mm inferior to the corneoscleral limbus. Approximately 5% to 13% of adult populations worldwide experience ptosis.¹ The underlying etiology for ptosis is broad with a wide range of acuity, making management of ptosis in the emergency setting challenging. In addition, the severity of ptosis does not always correlate with the degree of pathology or risk to vision and health. Furthermore, patients may not be aware of the time of onset of ptosis and may not present until their eyelid obstructs the visual axis or has significantly decreased their quality of life.

PATHOPHYSIOLOGY

Elevation of the upper eyelid requires coordination of the structural musculature and nervous components that innervate them. The tarsal plates (connective tissue) provide the general structural integrity of the eyelids. Elevation of the upper eyelids occurs by coordinated action of the levator palpebrae superioris and the superior tarsal muscle (Müeller muscle). The oculomotor nerve (cranial nerve III) provides innervation to the levator palpebrae muscle, whereas the superior tarsal muscle receives innervation from the sympathetic fibers of the superior cervical ganglion. The frontalis muscle innervated by the facial nerve (cranial nerve VII) raises the eyebrows.

Disruption to any of the components responsible for upper eyelid elevation can cause ptosis. The pathophysiology can be dichotomously divided into congenital and acquired. This chapter concentrates on the underlying pathophysiology of acquired ptosis that will present in the emergency setting. Pathophysiology of acquired ptosis can be categorized as mechanical, aponeurotic, myogenic, neuromuscular junction, and neurogenic disorders.

Any mass occupying lesions (eg, orbital tumors) or eyelid cellulitis can cause ptosis that can be categorized under mechanical disruption. Thinning of the aponeurosis, caused by aging or iatrogenic intervention, of the levator palpebrae muscle contributes to the aponeurotic causes of ptosis. Myogenic causes of ptosis can involve mitochondrial dysfunction or underlying genetic defects that often cause bilateral ptosis as a result of skeletal muscle dysfunction. Neuromuscular junction causes of ptosis most commonly involve antibodies attacking the acetylcholine receptor (AChR) at the neuromuscular junction of the levator palpebrae muscle. Lastly, neurogenic disorders involve oculomotor nerve palsy or the disruption of the cervical sympathetic chain.

APPROACH/THE FOCUSED EXAM

In evaluating patients with ptosis, emergency providers should inquire about any history of trauma, the course of the lid droop (onset, progression, variation), the presence and nature of
eye pain, headache, and double vision. Patients should be asked about a history of eye surgery, eye drops, allergies, eye rubbing, and keratoconus, all of which can lead to eyelid retractor dehiscence.

A complete intraocular exam should be preceded by a cranial nerve exam, ocular motility exam, and evaluation of globe dystopia. Anterior displacement of the eye (proptosis or exophthalmos) should be noted, by either observation (“ant’s eye view” or “worm’s eye view”) or measurement (with an exophthalmometer). Orbital tumors are discussed in Chapter 29.

Careful examination of an acutely ptotic eyelid may reveal a focal eyelid lesion (eg, hordeolum or chalazion) or another process limited to the eyelid. A diffusely edematous pink eyelid associated with tearing and red eye suggests viral conjunctivitis, whereas an edematous lid with surface scale associated with itching is more likely to be allergic dermatitis. For many patients, it is impossible for them to distinguish whether the lid is drooping (ptosis) or swollen, and they may simply describe either condition as a “heavy” lid. Comparison with old photographs (eg, on a driver’s license or social media accounts) can be helpful to establish their baseline appearance. In some cases, a new presentation will be identified as a preexisting condition.

Specific measurements to precisely elucidate the ability of the upper eyelid to elevate include the margin reflex distance-1 (MRD1) and levator function (LF), also known as levator excursion. MRD1 measures the distance from the corneal light reflex (with a bright focal light source held at eye level) to the upper eyelid margin (Figure 34.1). LF, normally 15 to 20 mm, is measured by holding a ruler next to the patient’s eyelid margin when they are looking down and then measuring the maximal superior position of the eyelid when they are asked to look up while the examiner fixates their frontalis by pressing firmly on the forehead (Figure 34.2).

The most important elements of the intraocular exam for a ptotic patient are the pupillary exam: evaluate for anisocoria, direct response, consensual response, relative afferent pupillary defect (rAPD), visual acuity, and intraocular pressure. Decreased vision is generally not caused by ptosis alone, so some other cause must be found either on the intraocular exam or, if there is an rAPD, on the optic nerve/visual pathways.

In many acute presentations, neuroimaging is appropriate. A thin-sliced orbital computed tomography (CT) is sufficient for most cases of orbital trauma where the pathology is limited to the orbit, but magnetic resonance imaging (MRI) is the diagnostic modality best suited for deep orbital and intracranial pathology. If an autoimmune etiology is suspected, laboratory workup may be indicated.

Figure 34.1: The upper eyelid (MRD1); this is the distance in mm from the corneal light reflex to the upper eyelid margin. MRD2 = distance from the corneal light reflex to the lower eyelid margin. Ptosis is defined as a low MRD1 value. MRD, margin to reflex distance. (Courtesy of Harsha S. Reddy, MD.)

Figure 34.2: Levator function (levator excursion) is measured by aligning a ruler with the eyelid margin when the patient is looking down. The patient is then asked to look up (while the examiner looks up), and the maximal upper eyelid position is marked against the same ruler—in this case 13.5 mm. (Courtesy of Harsha S. Reddy, MD.)

DIFFERENTIAL DIAGNOSIS

The differential diagnosis for ptosis is extremely broad given the numerous possible underlying causes. Some common and possible dangerous presentations are highlighted here.

Aponeurotic Ptosis

Thinning and involution of the aponeurosis of the levator apparatus related to aging is by far the most common cause of acquired ptosis.¹ This often presents in the elderly with symmetric and bilateral ptosis. In the absence of focal eyelid/orbital signs, pupillary involvement, vision changes, extraocular motility defects, or other neurologic symptoms or findings, it is possible that the patient is suddenly noticing a long-standing ptosis.

Traumatic (Mechanical) Ptosis

Ptosis can result from edema/hemorrhage weighting down the eyelid (mechanical ptosis) or blunt trauma or transection of the levator aponeurosis/muscle or from a neurogenic cause (covered separately later). Mechanical ptosis is readily visible externally (Figure 34.3). Damage to the levator can be more subtle—suspicion should be high in any full thickness horizontal laceration above
the tarsus or any laceration in which orbital fat is visible in the upper eyelid. Blunt trauma to the levator is less well understood and can spontaneously resolve as late as 6 months post trauma. Measurement of LF and comparison with the unaffected side is helpful for diagnosis and monitoring for improvement. Occasionally, a process that causes enophthalmos such as an orbital floor fracture can give the appearance of ptosis (pseudoptosis) because the recessed position of the globe makes the palpebral fissure smaller.