## 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

<h3 id="aetiology-1">Aetiology</h3>
- 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

<HotTopic>
Tolosa-Hunt syndrome

- Idiopathic sterile inflammation of the cavernous sinus/orbital apex

- Marked ipsilateral ‘gnawing’ periorbital pain along with neuropathies of the nerves passing through the sinus (CN 3, 4, V1, V2, 6 and sympathetics)

- May present with visual loss

- Diagnosis of exclusion after infection, lymphoma and carcinoma have been excluded

- Episodes typically resolves over 8 weeks but can commonly recur after months to years

- MRI: enhancing lesions of intermediate density on T1 (can be difficult to distinguish from meningioma, lymphoma or sarcoidosis)

</HotTopic>

### Tests

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

<Note>
Apraclonidine 1% should not be used in children and apraclonidine 0.5% must not be used in patients under 6 months (and with caution under 2 years)
</Note>

- 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

<h3 id="aetiology-1">Aetiology</h3>

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

<h3 id="clinical-features-1">Clinical features</h3>

- 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

<h3 id="tests-1">Tests</h3>

- 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

<h3 id="clinical-features-2">Clinical features</h3>
- 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


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…

Neuro-ophthalmology

Anisocoria

Intro

FRCOphth Part 2 Study Notes

Tumours, masses and neoplasia

Tumours overview

Uveitis

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