Causes of mechanical ptosis include conjunctival, eyelid, or orbital masses; eyelid infections such as chalazia or cellulitis; eyelid hematomas; hemangiomas; or orbital roof fractures with inferior displacement of bony fragments.²,⁴,⁵ Although a true structural ptosis and dermatochalasis may coexist in the elderly, long-standing skin redundancy is an important cause of mechanical ptosis due to the relative extra weight of the excess skin.⁶ Traumatic cicatrization of the eyelid skin can also mechanically restrict the eyelid in a ptotic position although the levator muscle is essentially normal.⁷ Any of the aforementioned morbidities causing mechanical disturbance of the upper eyelid can result in an anatomic ptosis because they limit the ability of the levator muscle to elevate the eyelid due to the sheer weight or obstruction of a mass.

The most common causes of pseudoptosis are contralateral upper lid retraction and posterior globe dystopia.⁸,⁹ Contralateral eyelid retraction due to thyroid eye disease is by far the most common cause.² Enophthalmos or posterior displacement of the globe relative to the orbital rim can also cause a droopy eyelid due to lack of support from the retrodisplaced globe.⁸ This can be seen with structural abnormalities of the orbit causing orbital volume expansion (orbital fractures, absence of the sphenoidal wing in neurofibromatosis [NF-1], or silent sinus syndrome). Fibrotic orbital processes such as scirrhous carcinoma of the breast can cause posterior traction on the globe and enophthalmos with pseudoptosis. Enophthalmos can also be seen with conditions such as age-related lipoatrophy, trauma, or drug-induced prostaglandin-associated periorbitopathy²,¹⁰,¹¹ that can result in orbital fat atrophy allowing the globe to move posteriorly within the orbit. Posterosuperior migration or recession of the preaponeurotic fat into the orbit in the elderly population may also cause pseudoptosis.¹² Pseudoptosis can also be observed after aggressive upper eyelid blepharoplasty with excessive resection of the orbicularis muscle or the preaponeurotic fat.¹³ This sunken pseudoptotic appearance may take years to evolve after the original surgery. Globe size asymmetry from conditions such as microphthalmia or phthisis bulbi can present with a pseudoptosis.⁵,⁸ Other causes of pseudoptosis include essential blepharospasm, so-called apraxia of eyelid opening, hemifacial spasm, and even psychogenic eyelid closure,¹⁴ all of which cause a narrowing of the vertical palpebral fissure from spasm of the orbicularis muscle.

Apparent ptosis, on the other hand, is only the visual impression of a narrow palpebral fissure without a true
decrease in the MRD1. It can be caused by marked upper eyelid dermatochalasis, excessive brow ptosis with overhanging skin, or vertical strabismus so that the cornea is displaced upward beneath the eyelid margin.²,⁸ The illusion of ptosis can also be seen if the contralateral upper eyelid is relatively elevated in patients with unilateral axial myopia because the myopic eye is longer and more prominent. Upward globe dystopia (hyperglobus) due to an inferior orbital mass or a tumor extending from the maxillary sinus into the orbit may displace the eye upward so that the upper eyelid margin appears lower with respect to the cornea, resulting in a reduced MRD1²,⁸ even though the vertical palpebral fissure may be normal.