Anisocoria

Aetiology

• Physiological

  • 15-20% of population (but may be more common)
  • Defined as difference of 0.4mm or more in pupil size without pathological cause
  • Asymptomatic
  • Normal reactions otherwise

• Iris damage

• Pharmacological eg. hyoscine

  • Can be sympathetic or parasympathetic agents
  • Use pilocarpine (for large pupils) or tropicamide (for small pupils): failure to fully reverse the dilation/constriction confirms pharmacological anisocoria

• Sympathetic chain pathology

• Parasympathetic chain pathology

Horner’s syndrome

Clinical features

• Ptosis (1-2mm due to non-functioning Mullers)
• Miosis: normal light and near reaction. Most pronounced in the dark due to dilator dysfunction
• Apparent enophthalmos: due to small elevation of lower lid
• Facial anhidrosis: suggests lesion of first or second-order neurone (ie.proximal to the superior cervical ganglion
• Iris hypochromia: suggests congenital or long-standing lesion. Typically only develops from 9 months onwards. Not seen in blue iris individuals
• Reduced IOP

Anatomy

• First order neuron: cell bodies in the posterior lateral hypothalamus

  • Descends through the brainstem to the intermediolateral cell column between C7 and T2

• Second order neuron: projects to the paravertebral sympathetic chain

  • Fibers ascend to the superior cervical ganglion

• Third order neuron: cell bodies lie in the superior cervical ganglion

  • Project into the cranial cavity with the ICA in the carotid plexus, through the cavernous sinus
  • Travel along the abducens nerve before joining the nasociliary branch of V1, then through the ciliary ganglion (without synapsing) to the dilator muscle

Aetiology

• Most common (descending)

  • Surgery
  • Birth trauma
  • Mass lesion

• Central

  • Brainstem: CVA, tumour, demyelination

    • Wallenberg syndrome: ischaemic stroke of the dorso-lateral medulla (eg. via occlusion of the posterior inferior cerebellar artery). Causes loss of pain and temperature sensation on contralateral side and ipsilateral Horner’s syndrome (first order), as well as ataxia, vertigo, diplopia (skew deviation), hiccups

  • Spinal cord: tumour, syringomyelia, trauma

• Preganglionic

  • Lung apex trauma or tumour
  • Neck trauma, surgery, tumour or common carotid dissection

• Postganglionic

  • Internal carotid dissection
  • Otitis media or herpes zoster of the middle ear (Ramsay-Hunt syndrome)
  • Cavernous sinus thrombosis or tumour
  • Orbital tumour
  • Tolosa-hunt syndrome
  • Cluster headache

• Congenital Horner’s

  • May be idiopathic or due to birth trauma
  • Facial flushing/’harlequin’ sign on crying/exertion due to anhidrosis
  • Exclude neuroblastoma in children with acquired Horner’s: commonest extra-cranial tumour in children under 5

Tests

• Apraclonidine (weak alpha1 agonist as well as alpha2 agonist)): does not normally affect the pupil. Dilates a Horner’s pupil (soreversesanisocoria) and may reverse ptosis
  • Measure pupils in bright and dark ambient conditions
  • Instill apraclonidine to both eyes
  • Wait 1 hour then remeasure pupil sizes

• Cocaine (blocks reuptake of noradrenaline at the dilator pupillae NMJ): Horner’s pupil will fail to dilate (normal pupil dilates)

• Identifying the level

  • Hydroxyamphetamine: dilates a Horner’s from the first or second order neurones ie. pre-ganglionic (but not a lesion of the third order neurone)
  • Adrenaline will dilate a post-ganglionic lesion (1% phenylephrine can be used instead

• Urinary catecholamines and vanillylmendelic acid (VMA) in children to rule in/out neuroblastoma

• MRI brain/spinal cord/orbits

• CXR/CT chest

• Carotid doppler

• Lymph node biopsy

• ENT evaluation eg. if suspicion of middle ear disorder

Adie’s tonic pupil

Abnormal parasympathetic signal from the ciliary ganglion to the iris/ciliary muscle

Aetiology

• Thought to be due to viral denervation
• Local damage to the ciliary ganglion (may include sarcoid and GCA)
• Autonomic dysfunction including neurosyphilis
• Idiopathic

Clinical features

• Typically unilateral
• Healthy young women
• Mydriasis: poor light response
• Vermiform movements on slit-lamp
• Exaggerated, slow response to near
• Light-near dissociation: this is due to a 30:1 ratio of accommodative fibres to light responsive fibres. Therefore loss of light response is much more likely with relative preservation of accommodation.
• Absent deep tendon reflexes (Holmes-Adie syndrome)
• Corneal sensation may be reduced
• Over time, the chronic tonic pupils actually shrink and can become smaller than average

Tests

• 0.125% pilocarpine (dilute): greater response in Adie’s pupil due to denervation hypersensitivity

Idiopathic intermittent unilateral mydriasis

Transient mydriasis for 15-60 minutes Associated with migraine and more common in women.

Argyll Robertson pupils

Caused by tertiary neurosyphilis

Clinical features

• Unilateral then bilateral irregular miosed pupils
• Poor light reaction
• Light-near dissociation
• Atrophic iris

Management

• VDRL tests measure disease activity but may become negative in later stages
• FTA-ABS and haemagglutination tests detect current/previous infection
• High dose penicillin eg. benzathine benzylpenicillin in conjunction with GU physician
• Treatment may transiently worsen inflammation: Jarish-Herxheimer reaction