Ophthalmology SC012: Neuro-Ophthalmology Flashcards
Neuro-ophthalmic examination
- VA
- Snellen chart - Pupillary exam
- Colour vision
- Ishihara colour plates - VF
- Confrontation test
- Scotoma may be difficult to detect simply by confrontation - Ocular motility
- Ophthalmoscopy
- Direct / Indirect
- Last ∵ need to dilate pupil
***Neuro-ophthalmic problems
- Pupillary disorders
- Afferent
—> RAPD
—> Visual impairment
- Efferent
—> Anisocoria
—> LND
Diseases:
- Adie’s pupil
- Horner’s syndrome
- Argyll Robertson pupils
- Motility disorders
- CN3 palsy
- CN4 palsy
- CN6 palsy
- INO
- MG - Optic nerve disease
- Papilledema (although not optic neuropathy itself)
- Papillitis
—> “Typical” optic neuritis
—> “Atypical” optic neuritis - Ischaemic optic neuropathy (ION)
—> AION (Arteritic / Non-arteritic)
—> PION - Transient monocular visual loss (TMVL) (Amaurosis fugax)
- Optic atrophy
- VF defects
- Pupillary disorders
Classification:
- Afferent vs Efferent disorder
Afferent disorders S/S:
1. **RAPD (if unilateral / asymmetrical)
2. **Visual impairment (VA, colour vision, VF defect)
Causes:
- Optic neuropathies
- Severe retinopathies (less common e.g. Total RD, CRVO, CRAO)
Efferent disorders S/S:
1. **Anisocoria (unequal pupil size) **without RAPD (if unilateral / asymmetrical)
2. **Light near dissociation (LND)
- i.e. no constriction to light but can accommodate to near objects
- dorsal aspect of Edinger-Westphal nucleus affected while ventral aspect spared
- causes: e.g. Adie’s pupil, Argyll Robertson pupil
—> Adie’s pupil: Abnormally **unilateral **large pupil, Near response slow + prolonged
—> Argyll Robertson pupil: Abnormally **bilateral ***small pupil, Near response brisk + immediate
Diseases:
1. Adie’s pupil
2. Horner’s syndrome
3. Argyll Robertson pupil
RAPD
Most patients do not have anisocoria (usually only in severe optic neuropathy e.g. total transection of optic nerve)
- but most patients only have a few optic nerve fibres affected
—> no anisocoria
Use normal side of eye as baseline
—> swinging torch test
—> abnormal side will dilate when light shine on it
Anisocoria
Mostly due to ***Efferent disorders
- Check for obvious causes (History + P/E)
- Trauma (e.g. sphincter tear)
- Iritis (e.g. Posterior synechia)
- Medications (e.g. mydriatics, miotics)
- CN3 palsy
- Severe unilateral ***afferent disorder (e.g. optic atrophy, optic nerve transection leading to total absence of light perception) - Check which eye is abnormal
- Determine degree of anisocoria in **bright + **dim lighting conditions
—> Difference in size greatest in bright light = **Large pupil is abnormal
—> Difference in size greatest in dim light = **Small pupil is abnormal
Abnormally large / Dilated pupil
Commonly due to loss of **parasympathetic tone to pupil
1. **CN3 palsy
2. ***Adie’s / Tonic pupil
3. Trauma to orbital parasympathetics
Other causes:
4. Direct damage to iris sphincter (e.g. surgery)
5. Dorsal midbrain syndrome
6. Pharmacologic mydriasis
- Adie’s / Tonic pupil
- ***Benign idiopathic condition
- Adie’s syndrome: Benign ciliary ganglionopathy: damage to ***ciliary ganglion (CN3)
- Mostly ***unilateral + in young females
- Tonic (i.e. Abnormal) pupil larger under ambient (esp. bright) light
- ***Light near dissociation of tonic pupil
- If associated with generalised hyporeflexia in limbs —> Holmes-Adie syndrome
Confirmation test (when CN3 palsy ruled out e.g. EOM normal, no diplopia, no ptosis):
Instillation of **weak cholinergic (0.1% Pilocarpine) in both eyes
- Tonic pupil constrict markedly (∵ **denervation hypersensitivity of the iris sphincters)
- Minimal / No effect on normal pupil (∵ pilocarpine concentration too low)
—> End result: “Reversal” of anisocoria after 30-60 mins
Abnormally small / Constricted pupil
Often physiological:
1. ***Physiologic anisocoria
- difference <=1 mm
- normal response to light + accommodation
- eye exam otherwise normal
Need to consider:
2. ***Horner syndrome
3. Argyll Robertson pupil (ARP)
- bilateral but may be asymmetrical
3. Pharmacologic miosis (e.g. Pilocarpine, Carbachol)
- Horner’s syndrome
Loss of ***sympathetic tone to affected eye
Types:
1. Central (1st order neuron)
- **Brainstem CVA / tumour
- **MS
- Pre-ganglionic (2nd order neuron)
- ***Apical lung lesion (e.g. Pancoast)
- Neck / thorax surgery
- Jugular vein cannulation - Post-ganglionic (3rd order neuron (along internal carotid artery))
- ***ICA dissection
- Neck surgery
- Tumours involving sellar / parasellar region
Triad of signs:
1. **Partial UL + “Inverse” LL ptosis (lower lid go upwards) (may have contralateral paradoxical UL retraction)
2. **Miosis + Dilation lag
3. ***Anhydrosis (Hemifacial) (only in Central / Pre-ganglionic, ∵ sympathetic to sweat gland already branched off along external carotid artery)
Other signs:
4. **Iris heterochromia
- in congenital case
- difference in iris colour —> **hypochromic iris in affected eye (∵ delay in development of pupil in affected eye)
Confirmation test for Horner’s
**Apraclonidine 0.5/1% (weak α1 agonist, used to ↓ IOP in glaucoma) in both eyes (Cocaine eye drops obsolete)
- Pupil dilation (30-45 mins) + UL retraction (5 min, ∵ not require absorption into eyeball) in affected eye (∵ **denervation hypersensitivity due to upregulation of α-receptors)
- Minimal / No effect on normal eye
—> End result: “Reversal” of anisocoria + ptosis
—> False negative if acute Horner’s (<1 week, ∵ takes time for denervation hypersensitivity to develop)
Localisation test for Horner’s (Optional)
Conduct >=1-2 days after confirmation test with apraclonidine:
- ***Hydroxyamphetamine 1% in both eyes, after an hour:
- Central + Pre-ganglionic lesions: Both pupils dilate (mydriasis of the pupil, ∵ post-ganglionic neuron is intact and therefore able to release NE)
- Post-ganglionic lesions: Affected pupil fails to dilate (∵ NE not available to be released in affected post-ganglionic nerve endings)
(Hydroxyamphetamine: sympathomimetic which stimulates release of stored endogenous NE from the postganglionic axon terminals into neuromuscular junction at iris dilator muscles)
OR
- ***Phenylephrine 1% (very weak) in both eyes, after an hour:
- Central + Pre-ganglionic lesions: Both pupils remain undilated
- Post-ganglionic lesions: Affected pupil dilates (∵ denervation hypersensitivity)
Imaging investigations for Horner’s
New, recent onset:
- MRI **base of brain to mid-thorax
- Urgent angiographic imaging **CTA / MRA for suspected carotid artery dissection esp. if acute onset with pain on neck / face / head
Chronic:
- Most will have normal imaging (considered idiopathic / benign e.g. congenital Horner)
Light Near Dissociation (LND)
- ∵ Lesion affecting midbrain
- Accommodative response preserved (ARP), Pupillary response absent (PRA)
Causes:
Bilateral
1. True Argyll Robertson pupils (AR pupil)
- from **Neurosyphilis
2. Pseudo-AR pupil
- DM
- Parinaud’s syndrome
- Myotonic dystrophy
- Alcoholism
—> Bilateral LND should have **Serologic testing for syphilis + ***MRI brain (including brainstem)
Unilateral
1. Adie’s pupil
2. Aberrant regeneration of CN3 after CN3 palsy
- Motility disorders
S/S:
- Diplopia
Diseases:
1. CN3 palsy
2. CN4 palsy
3. CN6 palsy
4. INO
5. MG
Diplopia
History:
- Binocular (Neuro-ophthalmic disorders) / Monocular (Eye disorders)
- Persistent / Transient (Diurnal? —> MG)
- Sudden (Vascular causes e.g. Ischaemic mononeuropathy) / Gradual + Progressive onset (e.g. Tumour)
- Horizontal (e.g. CN6 palsy) / Vertical / Diagonal (e.g. CN3 palsy) / Rotational separation
- Painless / Painful
- Same / Varying amount of image separation with different gaze positions (Concomitant vs Incomitant squint)
Treatment:
1. ***Fresnel prism
- realignment of visual axis (in vertical and horizontal diplopia but not in torsional)
- orientation described as “base-out” vs “base-in” (eg. base-out prism used in CN6 palsy to deviate light medially)
- Unilateral occlusion (Patching) of poor eye if unsuccessful
