17.1 Introduction

Involutional ptosis describes the subset of acquired blepharoptosis most commonly due to stretching or disinsertion of the levator aponeurosis. ¹ The appearance is classically characterized by a decrease in margin reflex distance 1 (MRD1), normal levator function, elevated upper eyelid crease and fold, and decreased palpebral fissure in downgaze.

Involutional ptosis is the most common etiology for ptosis encountered in an oculoplastic practice, found to make up greater than 60% of ptosis cases in large tertiary referral centers. ² The prevalence of involutional ptosis increases with age, with average age of presentation in the seventh decade of life; however, younger patients can be affected. ² ID#b638a848_3 ^{– 4} Patients with this condition often present with consequent visual field complaints and concern about aesthetic appearance. Appropriate assessment to rule out other causes of acquired ptosis is essential. In this chapter, we provide information to understand and manage involutional blepharoptosis.

17.2 Etiology

Involutional ptosis is most commonly due to disinsertion or attenuation of the levator aponeurosis. Intraoperative anatomical findings may also include a lateral shift of the tarsal plate and dehiscence of the medial limb of Whitnall’s ligament. ⁵ Intraoperative and histopathological observations of these patients have noted a small subset with fatty degeneration of levator muscle, which may point to a concurrent myopathic component in some cases. ⁵

Classic associated risk factors for the development of involutional ptosis include habitual eyelid rubbing, contact lens use, and history of ocular procedures or surgery. Frequent lid rubbing in patients with irritation due to keratoconjunctivitis, blepharitis, or dry eye can contribute to microtrauma to the levator complex. Similarly, patients that wear hard or soft contact lenses may have chronic microtrauma to the levator muscle during lens placement, lens removal, and blink, contributing to levator dehiscence over time ⁶ (Fig. 17.1). Chronic eyelid inflammation may also contribute to levator disinsertion ⁷ (Fig. 17.2). Blepharochalasis syndrome, a condition characterized by recurrent, idiopathic episodes of upper eyelid edema, has an association with both primary and recurrent involutional ptosis. ⁸

Blepharoptosis that develops after ocular surgery can involve disinsertion of the levator aponeurosis and thereby may be considered a subset of involutional ptosis. Postoperative ptosis may result less commonly from myogenic, neurogenic, or mixed mechanism changes. ⁹ Etiologic factors for postoperative ptosis may be multifactorial and include soft tissue inflammation, anesthetic myotoxicity, or iatrogenic trauma to the levator muscle (Table 17.1). Ptosis has been reported after a wide spectrum of ocular surgeries, including cataract, glaucoma, vitreoretinal, pterygium, and refractive operations. The incidence of ptosis after intraocular and ocular surface surgeries averages 6% (range: 4–21%). ^{10 ,​ 11} Usually, eyelid ptosis is transient and lasts less than 6 months. ¹² Changing the technique of cataract surgery from extracapsular cataract extraction to phacoemulsification has significantly reduced the incidence of postcataract surgery ptosis. ¹³ Additionally, dehiscence of the levator aponeurosis has also been observed after sub-Tenon’s injection of corticosteroids. ^{14 ,​ 15}

17.3 Clinical Presentation

Patients with involutional ptosis typically present with unilateral or bilateral decreased palpebral fissure, decreased palpebral fissure on downgaze, decreased MRD1, elevated upper eyelid crease and fold, and normal levator excursion (LE) ¹⁶ (Fig. 17.3). These patients may demonstrate chronic frontalis activation and eyebrow elevation to compensate eyelid ptosis. Thus, relaxation of the frontalis muscle by cosmetic botulinum toxin to the forehead may unmask or aggravate eyelid ptosis. In some patients with levator disinsertion and fair skin, the iris and pupil may be visible through the eyelid skin. Additionally, a subset of patients with involutional blepharoptosis may demonstrate eyelash ptosis. ¹⁷

Presenting symptoms vary in severity and range from minor cosmetic concern to visual significance. Patients with visual field obstruction may complain of a superior or peripheral visual field deficit or difficulty reading, as the eyelid droops in downgaze. ¹⁸

Cosmetic complaints are often related to anatomic changes in the aesthetic subunits of the eyelid–brow complex, including eyelid or brow height, margin fold asymmetry, or associated dermatochalasis (Fig. 17.4). Additionally, some patients may complain of cephalgia or forehead fatigue as a result of chronic frontalis muscle contraction.