neuro-opthamology Flashcards
what makes CNII
formed by the convergence of retinal ganglion cell axons
what are the four parts of CNII optic/nerve
- Intraocular (shortest; 1 mm): Exits posteriorly via the lamina cribrosa (scleral opening).
- Intraorbital (longest; 25 mm): Has myelinated covering. Ends at the optic foramen.
- Intracanalicular: Where the optic nerve exits the orbit through the optic canal to enter the middle cranial fossa.
- Intracranial: Ends at the optic chiasm.
CNII blood supply
● Intraocular: Short posterior ciliary artery.
● Intraorbital to intracranial: Pial vessels of ophthalmic artery.
location of chiasm
anterior to the hypothalamus and usually directly superior to the pituitary gland.
what is junctional scotoma
anterior chiasmal lesions
ipsilateral optic neuropathy with contralateral superotemporal defects.
A few photosensitive retinal ganglion cell axons connect with the suprachiasmatic nucleus of the hypothalamus. This is important for the body’s circadian rhythm.
what is the optic tract
connect the optic chiasm with the lateral geniculate nuclei (LGN). The optic tract conveys signals from the contralateral nasal retina and the ipsilateral temporal retina.
Where is the oculomotor nerve based
dorsal midbrain at the level of the superior colliculus
motor functions of the oculomotor nerve
● Ipsilateral innervation to IO, IR and MR.
● Contralateral innervation to SR.
● Bilateral innervation to levator muscle.
pathway of oculomotor nerve
CNIII exits the brainstem through the interpeduncular fossa, passing between the posterior cerebral artery and superior cerebellar artery. Along its path, it travels near the uncus of the temporal lobe, making it vulnerable for compression in cases of uncal herniations. It then travels through the lateral wall of the cavernous sinus superior to CNIV and bifurcates into a superior and inferior branch at the anterior aspect of the sinus.
It enters the orbit through the SOF within the annulus of Zinn. The superior branch innervates the SR and the levator muscle, while the inferior branch innervates the MR, IR and IO.
CNIII is accompanied by parasympathetic fibres originating from the Edinger- Westphal nuclei, located in the midbrain dorsal to oculomotor nuclei, which innervates the sphincter papillae and ciliary body muscles.
pathway of oculomotor nerve
CNIII exits the brainstem through the interpeduncular fossa, passing between the posterior cerebral artery and superior cerebellar artery. Along its path, it travels near the uncus of the temporal lobe, making it vulnerable for compression in cases of uncal herniations. It then travels through the lateral wall of the cavernous sinus superior to CNIV and bifurcates into a superior and inferior branch at the anterior aspect of the sinus.
It enters the orbit through the SOF within the annulus of Zinn. The superior branch innervates the SR and the levator muscle, while the inferior branch innervates the MR, IR and IO.
CNIII is accompanied by parasympathetic fibres originating from the Edinger- Westphal nuclei, located in the midbrain dorsal to oculomotor nuclei, which innervates the sphincter papillae and ciliary body muscles.
pathway of the pupillary light reflex
The fibres involved in the pupillary pathway originate from the retinal ganglion cells. Those fibres exit the optic tract before reaching the LGN and enter the midbrain to synapse on the ipsilateral pretectal nucleus. The pretectal nuclei project bilateral fibres to the contralateral and ipsilateral Edinger-Westphal nuclei.
Preganglionic parasympathetic fibres from Edinger-Westphal travel along with CNIII and then exit the inferior branch of CNIII to synapse on the ciliary ganglion. From the ciliary ganglion, postganglionic parasympathetic fibres are carried via the short ciliary nerves to innervate the ciliary body muscle and sphincter pupillae.
what is the accomodation reflex
Accommodation is the adaptation of the eye when focusing on a near object. It works by:
- Increasing lens curvature: The ciliary body muscles contract via parasympathetics from Edinger-Westphal, leading to relaxation of the lens zonules.
- Pupil constriction: Activation of the sphincter pupillae via parasympathetics form Edinger-Westphal.
- Eye convergence: Contraction of medial recti via CNIII.
location and role of trochlear nerve
The trochlear nuclei are located in the midbrain at the level of the inferior colliculus. Each trochlear nucleus innervates the contralateral SO muscle.
CNIV passes through the lateral wall of the cavernous sinus inferior to CNIII and enters the SOF above the common tendinous ring.
characteristics of CNIV
● Only cranial nerve to exit dorsally from the brainstem.
● Smallest cranial nerve in number of axons.
● Longest unprotected intracranial course.
pathway of the abducens nerve
The abducens nucleus is located in the pontine tegmentum ventral to the fourth ventricle. The nucleus is located near the paramedian pontine reticular formation (PPRF) and surrounded by looping fibres of CNVII. CNVI exits the brainstem at the pontomedullary junction and crosses over the petrous apex of the temporal bone through an osteofibrous channel, called Dorello’s canal. It is at the Dorello’s canal where CNVI is susceptible to stretching in cases of increased intracranial pressure. CNVI then travels through the cavernous sinus, lateral to the internal carotid. It then enters the orbit via the SOF, through the tendinous ring, to innervate the LR muscle.
pathway for pupillary dilatation
- First-orderneurons:Startattheposterolateralhypothalamusandsynapseatthe intermediolateral cell column between C8 to T2 (ciliospinal centre of Budge).
- Second-order preganglionic neurons: Leave centre of Budge, travel over the lung apex and synapse at the superior cervical ganglion at the carotid bifurcation. This is where sudomotor fibres exit to course with the external carotid and supply the sweat glands of the face.
- Third-order postganglionic neurons: Travel around the internal carotid artery to finally innervate the dilator pupillae via long ciliary nerves (branches of the nasociliary nerve).
what is the SNS responsible for
pupillary dilatation and contraction of Müller muscle.
voluntary movements of they eye are initiated where
frontal eye field (FEF), Brodmann area 8, in the frontal lobe.
eye reflex movements are coordinated where
coordinated via the occipital cortex and superior colliculus in response to a visual stimulus.
what are the three types of movements in supranuclear motor
- Saccadic eye movements
- Smooth pursuit movements
- Vestibulo-ocular movements
define saccades
Saccades are fast eye movements which involve the rapid fixation of a desired object onto the fovea with abrupt change of point of fixation when switching from one object to the next. Saccades can have an angular speed of 600°/s, lasting around 30–100 milliseconds after a latency (time it takes to initiate) of approximately 200 milliseconds
what is smooth pursuit
This refers to slow movements of the eye designed to keep a moving stimulus fixed at the fovea. They have a latency of about 100 milliseconds, and a much slower velocity than saccades. They are initiated from parieto-occipital areas
what is vestibulo-ocular movements
These eye movements stabilize the eye relative to head movements. When moving the head, with eyes fixed on an object, sensory information of the semicircular canals results in the movement of the eyes in the opposite direction to the head movement. This occurs via projections from the vestibular nuclei to cranial nerves and PPRF.
what is optic neuropathy
refers to damage of the optic nerve
what is optic atrophy
longstanding damage to the optic nerve
common signs of optic nerve dysfunction
- Decreased visual acuity (dVA)
- Dyschromatopsia
- Visual field defects: Central scotomas, arcuate or altitudinal defects 4. Diminished contrast sensitivity
- Absolute or relative afferent pupillary defect (RAPD)
what are the three types of optic neuritis
retrobulbar
palpillitis
neuroretinitis
what is reterobulblar retinitis
a. The optic nerve behind the globe is affected.
b. The optic nerve head is not involved, giving rise to a normal-looking
optic disc on funduscopy. c. More common in adults.
what is palpillitis
a. Hyperaemia and oedematous optic disc with associated peripapillary
flame-shaped haemorrhage.
b. The optic nerve head is affected.
c. More common in children, typically in post-viral infections.
what is neuroretinitis
a. Papillitis with involvement of the retina.
b. Occurs in cat scratch disease and Lyme disease.
what is demyelinating optic neuritis
most common form of optic neuritis. It can occur in isolation or with conditions such as multiple sclerosis (MS) or neuromyelitis optica (Devic disease).
what is MS
autoimmune inflammatory disorder characterized by demyelination of the CNS. It has a female predominance and mainly presents in the third or fourth decades of life. MS is also more common in countries further away from the equator.
systemic features of MS
● Paraesthesia.
● Muscle cramping and weakness.
● Bladder, bowel and sexual dysfunction.
● Cerebellar dysfunction: Tremor + dysarthria + ataxia (Charcot’s triad).
● Lhermitte sign: Electrical shock on neck flexion.
● Uhthoff phenomenon: Symptoms worsen when body temperature increases
(e.g. hot shower).
opthalmic features of mS
● Retrobulbar optic neuritis: Acute onset of unilateral retrobulbar pain exacerbated by eye movements, dVA, central scotoma, dyschromatopsia and RAPD. This is followed by a spontaneous resolution after a few months (3).
● Internuclear ophthalmoplegia.
● Nystagmus.
Ix for MS
● MRI: Demyelinating plaques disseminated in space and time.
● Lumbar puncture: Oligoclonal bands in CSF.
Mx for MS
Intravenous methylprednisolone for 3 days followed by oral prednisolone for 11 days. This regimen resulted in a faster recovery and significant improvement in contrast sensitivity, colour vision and visual field compared to the oral prednisolone and placebo groups. However, methylprednisolone had only a slightly better but nonsignificant outcome in VA
what is neuromyelitis optica and what can be found
A demyelinating disorder characterised by severe retrobulbar optic neuritis and transverse myelitis in three or more vertebral columns causing muscle weakness, increased tone and spasms. IgG antibodies against astrocytic aquaporin-4 (AQP4) can be found.
what is neuroretinitis
Inflammation of the optic nerve with oedema spreading from the optic nerve head along the papillomacular bundle to reach the macula. Formation of exudates around macula gives a ‘macular star’ appearance.
neuroretinitis is caused by and causative organism
cat- scratch disease:
● Organism: Bartonella henselae (Gram-negative rod).
trasmission of neuroretinitis
Cat scratch or bite.
features of neuroretinitis
- Fever and lymphadenopathy
- Neuroretinitis: Unilateral, painless decrease in VA, papilitis, mild optic nerve dysfunction and star pattern of macular exudates
- Uveitis
- Granulomatous conjunctivitis
features of neuroretinitis
- Fever and lymphadenopathy
- Neuroretinitis: Unilateral, painless decrease in VA, papilitis, mild optic nerve dysfunction and star pattern of macular exudates
- Uveitis
- Granulomatous conjunctivitis
what is anterior ischaemic optic neuropathy (AION)
occurs due to damage to the optic nerve as a result of ischaemia. It can cause optic neuropathy in the elderly due to occlusion of the short posterior ciliary artery. It can be split into non-arteritic and arteritic
Aetiology of non-arteritic AION
Hypertension, diabetes, sleep apnoea or a physiologically small or absent cup (structural crowding of the optic nerve head)
vision loss in non-arteritis AION
Sudden Painless Unilateral VA usually >6/60 Visual field defect: Often inferior or superior altitudinal defects
Disc findings in non-arteritic (AION)
Usually segmental
hyperaemic disc swelling with peripapillary splinter haemorrhages
Ix for non-arteritic AION
Blood pressure, blood sugar, examination of optic disc and exclude GCA
FA: Delayed optic disc filling
Mx for non-arteritic AION
Treat underlying cause
aetiology of arteritic AION
due to GCA
vision loss in arteritic AION
Sudden Painful Unilateral with high risk to fellow eye if untreated Severe visual loss with VA <6/60
Disc findings in arteritic AION
‘Chalky-white’ diffuse swollen
disc
associated Sx of arteritic AION
Scalp tenderness, headache and jaw claudication
Ix for arteritic AION
ESR, CRP and temporal artery biopsy (specific but sensitivity can be low due to ‘skip lesions’)
FA: Delayed choroidal and optic disc filling
Mx for arteritc AION
High-dose IV methylprednisolone followed by oral prednisolone
what is leber hereditary optic neuropathy
A mitochondrial inherited disease caused by ganglion cell degeneration.
It mainly presents in young males aged 10–30 years. No effective treatment is available.
features of leber hereditary optic neuropathy
● Unilateral initially with bilateral ocular involvement over weeks to months.
● Painless visual loss.
● Central or centrocaecal scotomas.
● Triad of disc ‘pseudo-oedema’, peripapillary telangiectasia and tortuosity of
the medium-sized retinal arterioles
● Optic atrophy occurs in late disease.
Ix for leber hereditary optic neuropathy
● Family history and genetic testing.
● Optical coherence tomography (OCT): Can show optic nerve oedema (early) or atrophy (late).
causes of nutritional optic neuropathy/tobacco-alcohol amblyopia
vitamin B
copper and folic acid deficiencies
medications (e.g. ethambutol, amiodarone or sildenafil)
other toxic causes (smoking and alcohol).
features of nutritional optic neuropathy
● Gradual, progressive and painless bilateral dVA and centrocaecal scotomas.
● Dyschromatopsia.
what is papilloedema
Bilateral optic disc swelling secondary to raised intracranial pressure (ICP).
causes of papilloedema
- tumours
- haemorrhages
- hydrocephalus
- idiopathic intracranial hypertension (a diagnosis of exclusion, typically occurs in young, obese females).
features of increased ICP
● Headache (worse in the morning) with nausea and/or vomiting.
● Pulsatile tinnitus.
● Unilateral or bilateral transient visual loss with a duration of seconds.
● Enlarged blind spot.
● Diplopia due to CNVI palsy (less common).
● Hypertension + bradycardia + bradypnea (Cushing reflex).
● Optic disc signs
Hyperaemia and blurred margins of optic disc (early)
Swelling and elevation of the whole optic disc with peripapillary haemorrhages (late)
what is titlted discs
● Bilateral, small optic discs tilted inferonasally.
● Associated with high myopia.
● Superotemporal field defects are common.
what is morning glory anomaly, characterised, associated
● Unilateral and causes severe dVA.
● Characterized by a funnel-shaped excavation of the optic disc and
surrounding retinal tissue. Characteristically, the retinal vessels emerge from
the periphery of the optic nerve head rather than from the centre.
● Associated with retinal detachment.
what is optic disc pit and its complications
● Characterized by a greyish oval depression in the optic nerve head, usually located temporally.
● Complications: Exudative retinal detachment.
what is optic disc coloboma
● Occurs due to defect in embryonic fissure closing.
● Can be sporadic or associated with Goldenhar syndrome, microphthalmos,
CHARGE syndrome and many others.
● Glistening white bowl-shaped excavation of the disc (inferior part
predominantly affected) causing superior field defects and dVA.
what is optic disc drusen
● Collection of mucoproteins and mucopolysaccharides that progressively calcify in the optic disc. They present as yellow or white bodies on the optic disc.
● Commonly bilateral.
● Varying degrees of blurring/visual loss.
● Associations: Retinitis pigmentosa and angioid streaks.
what is optic nerve hypoplasia
Caused due to underdevelopment of the optic nerve. Patients often present with varying degrees of visual loss and a double-ring sign
risk factors of nerve hypoplasia
genetic diseases
maternal use of recreational drugs, smoking
alcohol.
what is anisocoria
presence of asymmetrical pupillary size between the two eyes. It can be physiological or pathological. The normal pupil size is between 2–4 mm in light conditions and 4–8 mm in the dark
less than 1–1.5 mm in diameter and is unchanged in light and dark environments.
what is horner syndrome
Caused by a lesion to the sympathetic pathway
horners is characterised by
● Ptosis: Mild eyelid drooping due to Müller muscle dysfunction.
● Miosis: Due to dysfunction of the dilator pupillae. The pupil reacts to light
and near stimuli.
● Ipsilateral facial anhidrosis: Not present in third-order neuron lesions.
● The affected iris in congenital Horner syndrome has a lighter colour.
causes of horner syndrome
● First order: Stroke Syringomyelia Multiple sclerosis Tumour Encephalitis Lateral medullary syndrome
● Second order: Pancoast's Tumour Thyroidectomy Trauma Cervical rib
● Third order: Carotid artery dissection Carotid aneurysm Cavernous sinus thrombosis Cluster headache
Ix for horner syndrome
topical apraclonidine
topical cocaine
topical hydroxyamphetamine
CT or MRI
how is topical apraclonidine used in horners Ix
confirm horners pupil
Apraclonidine is an alpha-2 and alpha-1 adrenergic agonist. Causes pupillary dilation in the Horner’s pupil due to denervation supersensitivity
how is topical cocaine used in horners Ix
Used to confirm a Horner’s pupil.
Cocaine blocks the reuptake of noradrenaline.
Causes a pupillary dilation of the normal pupil more than the Horner’s pupil
how is topical hydroxyamphetamine used in horners Ix
Used to differentiate a preganglionic from a postganglionic Horner’s pupils.
Hydroxyamphetamine releases norepinephrine from normal postganglionic adrenergic nerve endings, causing pupillary dilation.
Failure of dilation if the lesion is postganglionic (third order); however, first- and second-order neurone lesions will dilate.
what is seen in CT/MRI in horners
If tumours or carotid dissection/aneurysm are suspected.
what is Adie’s pupil
A unilateral condition characterized by loss of postganglionic parasympathetic innervation to the iris sphincter and ciliary muscle.
features od Adies pupil
● A large pupil with poor response to light but intense pupillary response (miosis) to near stimuli with slow re-dilation (light-near dissociation: pupil reaction to a near stimulus is greater than its reaction from a light stimulus).
● Holmes-Adie syndrome: Associated diminished deep tendon reflex of lower limbs.
Ix for Adie’s pupil
● Slit lamp: Vermiform movements of pupillary borders.
● Pharmacological: 0.1% (low dose) of topical pilocarpine into both eyes causes
constriction of the affected pupil due to denervation hypersensitivity.
what is Argyll Robertson pupil
Characterized by bilateral, irregular small pupils. Both pupils do not react to light; however, they constrict normally on accommodation (light-near dissociation). The most common cause is diabetes; it was previously neurosyphilis.
central lesions for horners Sx and causes
anhidrosis of the face, arm and trunk
stroke Syringomyelia Multiple sclerosis Tumour Encephalitis
preganglion lesions for honrers Sx and causes
anhidrosis of the face
Pancoast tumor
Thyroidectomy
trauma
cervical rib
postganglionic lesions for horners Sx and causes
no anhidrosis
Carotid artery dissection
Carotid aneurysm
Cavernous sinus thrombosis
Cluster headache
what do cotton wool spots represent in diabetic retinopathy
retinal infarction
