4.1 Introduction

Mechanical ptosis is the inferior displacement of the upper eyelid due to the mass or restrictive effect of an acquired eyelid or orbital lesion. The eyelid’s neuromuscular retraction system remains intact but is unable to overcome an opposing force generated by the mass or restrictive process. Mechanical ptosis is often readily identifiable on clinical examination and easy to differentiate from more common causes of ptosis such as involutional, myogenic, or neurogenic etiologies. Medical or surgical treatment for mechanical ptosis is directed at the underlying disease process.

4.2 Benign Eyelid Lesions

Any space-occupying lesion of the eyelid has the potential to cause mechanical ptosis. The amount of ptosis depends on the location and size of the lesion. Examples of benign eyelid lesions that may cause mechanical ptosis include infantile hemangiomas, chalazia, and plexiform neurofibromas.

Infantile hemangiomas are benign proliferations of capillary endothelial cells that frequently occur on the face and periocular region. They typically present in the first few months of life as a rapidly enlarging vascular lesion commonly involving the superomedial or medial aspect of the upper eyelid of an infant (Fig. 4.1). After an initial proliferative phase of approximately 6 months, these lesions often stabilize and spontaneously regress at 1 year of age. Small, clinically insignificant eyelid hemangiomas may be observed without intervention. Larger lesions causing ocular morbidity, such as mechanical ptosis, visually significant astigmatism, or occlusion of the visual axis, should prompt the clinician to consider intervention. Treatment in these cases is aimed at improving cosmesis and preventing refractive or occlusion amblyopia.

First-line therapy for patients with an infantile hemangioma is oral propranolol at a dose of 1 to 3 mg/kg/day through the proliferative phase or approximately 4 to 6 months. ¹ Topical timolol maleate is a viable alternative for superficial eyelid lesions. Both propranolol and timolol maleate are well tolerated and highly effective at inducing tumor regression. A thorough cardiac evaluation should be performed prior to initiation of β-blocker therapy and the infant should be monitored for cardiac events throughout treatment. Treatment options for lesions refractory to β-blocker therapy include surgical excision or intralesional corticosteroids.

Chalazia are a common cause of mechanical ptosis (Fig. 4.2). If large enough to affect the eyelid’s position, visual dysfunction usually results not from occlusion of the visual axis but induced corneal astigmatism. Initial treatment consists of warm compresses and gentle pressure to promote drainage of the lesion. If noninvasive therapy fails, intralesional injections of triamcinolone or curettage may be indicated. Intralesional corticosteroids are best reserved for those with small chalazia and fair skin. Incision and curettage is a better option for those with larger lesions or darker skin types. Recurrent chalazia warrant biopsy to rule out an occult malignant neoplasm.

Plexiform neurofibromas of the eyelid occur almost uniformly in association with neurofibromatosis type 1. This diffusely infiltrating lesion tends to involve the lateral aspect of the upper eyelid margin, giving it a characteristic S-shaped contour. Large eyelid plexiform neurofibromas may cause mechanical ptosis, corneal astigmatism, occlusion amblyopia, or psychosocial morbidity from poor cosmesis and low self-esteem (Fig. 4.3). Minimizing the risk of amblyopia and improving physical appearance are the most common indications for intervention. Treatment involves surgical debulking, though their infiltrative nature and lack of encapsulation make plexiform neurofibromas challenging to manage. At the time of surgery, levator dehiscence and lateral canthal tendon disinsertion are frequently encountered and often require repair. ² Long-term complications are usually related to tumor recurrence, particularly in children under 10 years of age. ³

4.3 Malignant Eyelid Lesions

Cutaneous malignancies, such as basal cell carcinoma, squamous cell carcinoma, sebaceous carcinoma, and melanoma, may present on the eyelid with mechanical ptosis. Of these, basal cell carcinoma is the most common and accounts for more than 90% of all periorbital skin cancers. Morbidity is almost always due to local invasion into adjacent structures. Tumors large enough to cause mechanical ptosis typically have been present for many years and may have already invaded the orbit (Fig. 4.4). Because basal cell carcinoma occurs most commonly in the elderly, younger patients presenting with basal cell carcinoma should raise suspicion for basal cell nevus syndrome, xeroderma pigmentosum, or an immunosuppressed state. ⁴

Squamous cell carcinoma of the eyelid occurs much less frequently than basal cell carcinoma. This lesion has a tendency to spread via perineural or lymphatic invasion. If an eyelid squamous cell carcinoma is large enough to cause mechanical ptosis, it is important to palpate regional lymph nodes and consider perineural spread. ⁵

Sebaceous carcinoma is a rare but highly lethal neoplasm of the eyelid’s sebaceous glands. It occurs more commonly in the upper eyelid, likely due to a greater number and concentration of sebaceous glands as compared to the lower eyelid (Fig. 4.5). Sebaceous carcinoma is known as a great masquerader, and its presentation may mimic chronic blepharitis, chalazia, or nonspecific inflammatory changes. Consequently, the diagnosis is often missed or delayed. ⁶ Rarely, other cutaneous malignancies, such as melanoma and Merkel cell carcinoma, present with mechanical ptosis. Like sebaceous carcinoma, these lesions have a high mortality rate and portend a poor prognosis.

The management for most malignant eyelid neoplasms is complete surgical excision with eyelid reconstruction. In contrast to medical therapy, excision allows for histologic confirmation of the diagnosis and definitive tumor clearance at the margin. Lesions large enough to cause mechanical ptosis typically require extensive tissue removal. Reconstructions are often challenging and require rotational flaps or skin grafts. The particular reconstructive procedure should be tailored to the size and location of the deficit. With regard to the mechanical ptosis, the upper eyelid position may elevate after lesion excision; however, residual ptosis may persist due to secondary mechanical ptosis from the bulk of the reconstructed flaps or grafts, cicatrization to the levator aponeurosis and muscle, or levator dehiscence after surgery.

Not all neoplastic eyelid lesions causing mechanical ptosis are primary tumors. Breast, lung, gastric, and prostate carcinoma as well as both cutaneous and uveal melanomas have been reported to metastasize to the eyelid. ^{7 ,​ 8} These lesions are typically small, solitary nodules but may become large enough to cause mechanical ptosis. Biopsy often reveals the diagnosis. Lymphoma, though classically associated with orbital disease, may also present with a facial mass or regional lymphatic obstruction producing periocular edema and a mechanical ptosis. ⁹ Treatment in all cases of systemic malignancy is aimed at the underlying disease and should be coordinated with an oncologist.