Ptosis: Causes and Pathogenesis

Ptosis

• Abnormally low position of the upper eyelid
• Caused by:
  • Mechanical factors:
    • Large lid lesions pulling the lid down
    • Lid oedema
    • Tethering of the lid by conjunctival scarring
    • Structural abnormalities, including disinsertion of the aponeurosis of the levator muscle
  • Neurological factors:
    • Third nerve palsy
    • Horner's syndrome due to a sympathetic nerve lesion
    • Marcus-Gunn jaw-winking syndrome (congenital mis-wiring of nerve supply)
  • Myogenic factors:
    • Myasthenia gravis
    • Muscular dystrophy
    • Chronic external ophthalmoplegia

Symptoms and Signs of Ptosis

• Cosmetic concerns
• Impaired vision
• Symptoms and signs associated with the underlying cause (e.g. asymmetric pupils, diplopia, reduced eye movements)
• Reduction in size of the palpebral aperture
• Upper lid margin may partially cover the pupil or the eye may be completely closed
• Elevated eyebrows as a compensatory event

Diagnostic Tests for Myasthenia Gravis

• Repeated elevation and depression of the eye results in increased ptosis
• Manual retraction of the upper lid causes ptosis or increased ptosis in the fellow eye
• Cogan's twitch test: look down for 15 seconds, then look up at an elevated target, and the lid overshoots and then falls slightly
• Ice test: apply ice to the lid for 2 minutes, significantly reduces myasthenic ptosis

Management of Ptosis

• Surgical correction in the absence of medically treatable disease
• Deferred in very young children, expedited if visual axis is covered and threatens amblyopia

Entropion

• Inturning of the lid margin and lashes towards the globe
• Usually occurs in the lower lid, especially in elderly patients with weakened orbicularis muscle
• Can be caused by conjunctival scarring, drawing the lid inwards (cicatricial entropion)
• Symptoms: marked irritation, red eye, corneal abrasion
• Short-term treatment: lubricants, taping the lid to turn lashes away from the globe
• Permanent cure: surgery or botulinum toxin injection into the orbicularis muscle

Ectropion

• Eversion of the lid away from the globe
• Caused by:
  • Age-related orbicularis muscle laxity
  • Scarring of the periorbital skin
  • Seventh nerve palsy
• Symptoms: malposition of the lids, everted puncta, epiphora