1187 Muscle in the Lower Eyelid Similar to Müller's Muscle in The

NORMAL ANDABNORMAL EYELIDFUNCTION 1187 muscle in the lower eyelid similar to Mu¨ller’s muscle in early stages, the ptosis may be barely evident in primary the upper eyelid (see above) results in elevation (‘‘upside- position, but because it typically worsens in downgaze, the down’’ ptosis) of the lower eyelid. The combination of ptosis eyelid may obstruct the visual axis when the patient attempts of the upper eyelid and elevation of the lower eyelid pro- to read (73–76). The presence of anisocoria (i.e., physiologic duces the appearance of enophthalmos, although exophthal- anisocoria that occurs in about 20% of normal individuals mometry invariably shows no asymmetry of the two eyes. [see Chapter 16]) or a mild and asymptomatic heterophoria, Other signs of Horner syndrome include ipsilateral facial or the frequent worsening of symptoms at the end of the anhidrosis in patients with first-order or second-order neuron day, may lead to the erroneous diagnosis of oculomotor lesions, mildly reduced intraocular pressure in the affected nerve palsy or myasthenia gravis in such patients (77). How- eye, heterochromia in congenital and very long-standing ever, the findings of normal levator excursion, an elevated cases, and an increased accommodation amplitude (Fig. or absent superior lid crease, a deep superior eyelid sulcus, 24.15). Horner syndrome is discussed in detail in Chapter worsening of ptosis in downgaze, and thinning of the skin 16 of this text. above the tarsal plate should distinguish an aponeurotic pto- The ptosis occasionally observed after conjunctival instil- sis from developmental, neurogenic, and myogenic causes lation of timolol maleate, a ␤-adrenergic blocking agent, (8,73,75,78,79) (Fig. 24.16). may be caused by Mu¨ller’s muscle blockade (70). Similarly, Levator aponeurotic defects commonly occur in the el- ␣ thymoxamine ( -adrenergic blocking agent) may cause pto- derly from involutional or degenerative changes that result sis when given topically or parenterally (71,72). in disinsertion, dehiscence, or thinning of the aponeurosis (80,81). Among patients between ages 15 and 50, aponeu- Ptosis from Disinsertion, Dehiscence, or Thinning of rotic ptosis is most commonly associated with a long history the Levator Aponeurosis of wearing rigid contact lenses. In such patients, repeated The most common cause of acquired ptosis in adults is a manipulation and traction of the upper eyelid while inserting dehiscence, disinsertion, or thinning of the levator aponeuro- or removing contact lenses causes disinsertion or thinning sis. Ptosis caused by such defects of the levator tendon may of the tendon (82–85). be bilateral or unilateral and can vary in its severity. In the Damage to the levator aponeurosis other than that associ- Figure 24.15. Appearance of Horner syndrome in four patients. A, Congenital right Horner syndrome. Note associated heterochromia iridis and minimal ptosis. B, Left Horner syndrome after neck trauma. C, Left Horner syndrome associated with apical lung (Pancoast) tumor. D, Left Horner syndrome in a patient with Raeder’s paratrigeminal neuralgia. 1188 CLINICAL NEURO-OPHTHALMOLOGY neurotic defects may also occur after episodes of eyelid edema caused by allergic reactions (81). In rare cases, congenital ptosis is caused by defects of the levator aponeurosis (95). Myopathic Ptosis Ptosis that occurs from damage to the levator palpebrae superioris muscle itself (as opposed to its tendon) may be either congenital (i.e., developmental) or acquired. Congenital Myopathic Ptosis (Developmental Ptosis) Although congenital ptosis occasionally is neurogenic (e.g., oculomotor nerve palsy, Marcus Gunn jaw-winking A phenomenon, Horner syndrome) or traumatic (e.g., from a forceps delivery) in origin, the most common form is caused by a developmental myopathy of the levator palpebrae superioris muscle. A decrease in striated muscle fibers, hyaline degeneration, fatty replacement, an increase in endomysial collagen, and loss of cross-striations characterize this disor- der histopathologically (81,96,97). Because developmental ptosis may worsen with age, it may not be noticed until early B Figure 24.16. Ptosis from levator dehiscence. A, Unilateral ptosis. Note the difference in location of the superior lid folds, with the left being much higher than the right. Also note the deepened superior sulcus on the left side. B, Bilateral ptosis from levator dehisence. Both eyelids show high superior lid folds and deep superior sulci. (Courtesy of Dr. Nicholas T. Iliff.) ated with contact lens wear can occur from trauma, including A that associated with ocular and orbital surgery. Thus, ptosis not infrequently occurs after cataract extraction, glaucoma surgery, radial keratotomy, orbital surgery, conjunctival pro- cedures, enucleations, strabismus surgery, and blepharoplasty. Ptosis following orbital surgery or blepharoplasty in which there is deep orbital fat dissection or supratarsal fixa- tion, is likely a result of direct injury to the levator aponeurosis. The aponeurosis also may be stretched or damaged from postoperative swelling, injection of an anesthetic into the upper eyelid, the use of a rigid lid speculum, ocular compres- sion and massage, or attempts by the patient to open the eyelid against a tight patch. The myotoxic effects of anesthetic injections and trauma to the levator itself from bridle sutures or retrobulbar injections may also play a role in some cases (79,85–93). In addition to the mechanisms described above, ptosis B from damage to or dysfunction of the levator aponeurosis Figure 24.17. Developmental (congenital) ptosis. A, When the patient may be associated with blepharochalasis, thyroid orbitopa- looks straight ahead, she has a very mild right ptosis. B, When the patient thy, pregnancy, and chronic use of topical steroids (9). Apo- looks down, there is mild lid lag on the right but not on the left..

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