Ptosis (Blepharoptosis)

Severe right ptosis with near-complete lid closure (Kanski's Clinical Ophthalmology)

Classification

Neurogenic Ptosis

• Horner syndrome: ptosis + miosis + anhidrosis. The affected eye has a smaller pupil. Caused by interruption of the oculosympathetic pathway (affects Müller's muscle). Full eye movements are preserved.
• CN III palsy: ptosis + larger or normal pupil + limitation of adduction, elevation, and depression. A pupil-sparing oculomotor palsy (normal pupil, limited adduction/elevation/depression) is also possible. Rarely, a lesion in the central CN III subnucleus causes bilateral ptosis with normal pupils and eye movements.

Myogenic Ptosis

• Myasthenia gravis: fluctuating ptosis that typically worsens late in the day or with sustained upgaze (fatigability). May be unilateral or bilateral, and can mimic virtually any ocular motility disorder.
• Chronic progressive external ophthalmoplegia (CPEO): symmetric, slowly progressive ptosis + limitation of eye movements from mitochondrial DNA mutations. Diplopia is a late feature because all eye movements are equally reduced. The Kearns-Sayre variant adds retinal pigmentary changes and cardiac conduction abnormalities.
• Oculopharyngeal dystrophy: autosomal dominant, onset in middle age; ptosis + limited eye movements + dysphagia.
• Myotonic dystrophy: autosomal dominant; ptosis, ophthalmoparesis, cataract, pigmentary retinopathy, muscle wasting, myotonia, frontal balding, and cardiac abnormalities.

Aponeurotic / Involutional Ptosis

• Eyelid swelling (infection, blunt trauma)
• Cataract surgery (mild post-op ptosis is common and usually resolves within a year without intervention)
• Long-term contact lens use

Mechanical Ptosis

Congenital Ptosis

• Absent or poorly defined upper eyelid skin crease
• Lid does not descend fully in downgaze (lid lag)
• Variable degree - mild to severe
• May be associated with superior rectus weakness (shared embryological origin)
• Risk of amblyopia (from visual axis obstruction or induced astigmatism)
• Refractive errors are actually more commonly responsible for amblyopia than the ptosis itself

Pseudoptosis

• Lack of globe support (enophthalmos, phthisis, artificial eye, microphthalmos)
• Contralateral lid retraction (makes one side appear relatively low)
• Ipsilateral hypotropia (lid follows the eye downward; resolves when the hypotropic eye fixates)
• Brow ptosis (confirmed by manually elevating the eyebrow)

Clinical Evaluation

• Palpebral fissure width (normal ~10-11 mm)
• Margin reflex distance (MRD1): distance from upper lid margin to corneal light reflex (normal = 4 mm; reduced in ptosis)
• Levator function (LF): excursion from maximal downgaze to maximal upgaze, with frontalis muscle neutralized by thumb pressure over the brow
  • Good: ≥8 mm
  • Fair: 5-7 mm
  • Poor: 4 mm or less
  • Absent: ~2 mm or less

Treatment

Surgical (definitive)

• Congenital ptosis: surgery during preschool years; earlier in severe cases to prevent amblyopia
• A weak Bell phenomenon (failure of the eye to rotate upward on lid closure) increases the risk of post-operative exposure keratopathy - check before surgery

Medical

• Myasthenia gravis: acetylcholinesterase inhibitors (pyridostigmine), immunosuppression, thymectomy
• Horner syndrome: identify and treat the underlying cause; phenylephrine eye drops can temporarily elevate the lid (pharmacological test and temporary treatment)
• Ptosis props / crutch spectacles: for patients unfit for surgery

Key Distinguishing Features at a Glance

Horner Syndrome (Oculosympathetic Palsy)

The three-neuron oculosympathetic pathway (Kanski's Clinical Ophthalmology)

Anatomy of the Three-Neuron Pathway

Classic Signs (the Triad + more)

Causes by Neuron Order

1st Order (Central)

• Brainstem stroke - lateral medullary (Wallenberg) syndrome is the classic cause
• Brainstem tumour or demyelination (MS)
• Syringomyelia / syringobulbia
• Cervical spinal cord lesion
• Diabetic autonomic neuropathy

2nd Order (Preganglionic)

• Pancoast tumour (apical lung carcinoma) - associated with T1 root involvement (weak hand intrinsics)
• Carotid or aortic aneurysm/dissection
• Thoracic spinal cord lesion
• Neck lesions: thyroid tumour, enlarged lymph nodes, trauma, post-surgical

3rd Order (Postganglionic)

• Internal carotid artery dissection - painful acute Horner syndrome; urgent vascular imaging required
• Cavernous sinus mass (thrombosis, aneurysm, tumour)
• Nasopharyngeal tumour
• Otitis media
• Cluster headache (migrainous neuralgia) - transient Horner during attacks

Clinical pearl: Acute onset of painful Horner syndrome - especially with neck or facial pain - should immediately raise concern for carotid artery dissection and be treated as an emergency.

Pharmacological Testing

Step 1: Confirm the Diagnosis

• Instill one drop in both eyes; check pupils at 30-45 min
• Result: Horner pupil dilates (and ptosis improves); normal pupil unaffected
• Mechanism: Alpha-1 receptors are upregulated (denervation supersensitivity) on the dilator pupillae in Horner syndrome, so apraclonidine (weak alpha-1 agonist) dilates it; the normal pupil has no such supersensitivity
• Sensitivity ~90%, specificity ~100%
• Caution: Do not use in infants (crosses blood-brain barrier). Has a ~7-day latent period before becoming positive in new lesions

• Result: Normal pupil dilates; Horner pupil does not
• Mechanism: Cocaine blocks noradrenaline reuptake at postganglionic terminals, causing dilation of a healthy pupil. In Horner syndrome, no noradrenaline is being secreted, so cocaine has no effect

Step 2: Localise Pre- vs Postganglionic

• Normal or preganglionic Horner: pupil dilates (functioning 3rd-order nerve releases NE)
• Postganglionic Horner: pupil does NOT dilate (3rd-order neurone is dysfunctional, no NE to release)

• Postganglionic Horner (established >10 days): pupil dilates and ptosis may improve (denervation hypersensitivity)
• Central/preganglionic and normal pupil: minimal or no dilation

Note: Do not perform sequential pharmacological tests within 3-5 days of each other (extended drug action)

Investigation

• Confirmed Horner syndrome → specialist neurological or neuro-ophthalmological referral
• Acute presentation = emergency - urgent imaging required
• Gold standard imaging: CT or MR angiography from aortic arch to circle of Willis (covers neck, carotid arteries, apical lung, thyroid, skull base)
• MRI with contrast if brainstem stroke suspected
• If features have been present >1 year with no other localizing signs, diagnostic yield from further investigation is very low
• Plain X-rays and carotid ultrasound have limited utility

Sweat Pattern for Localization

Bilateral Horner Syndrome

• Autonomic neuropathies
• High cervical cord transection
• Bilateral miosis may be subtle - pupillometry or observation of pronounced dilation lag when light is withdrawn helps detect it

Treatment

• Address the underlying cause
• The ptosis of Horner syndrome is mild; surgical correction can be considered at the patient's request
• Apraclonidine eye drops can be used as a temporizing measure to improve ptosis

Quick Comparison: Horner vs CN III Palsy vs Adie Pupil