Optic Nerve Head Flashcards
How are discs recorded?
• Drawing
• Which method used : Volk? 78D?
• C:D
• Rim/Disc
• Colour neuroretinal rim
• Margins - distinct, pigment and peripapillary atrophy
• Any other disc features
Common disc anomalies not part of disease processes:
• Myelinated nerve fibres
• Optic disc drusen
• Tilted optic disc
What are myelinated nerve fibres?
• The nerve fires are myelinated within the optic nerve and the myelin sheath usually stops at the lamina cribrosa
• 1% of population
- Unilateral in 80%
• Symptoms:
Usually asymptomatic
• Signs
- Fundus examination: Visible yellow patch of myelin around nerve head
- Visual fields: enlarged blind spot corresponding to area of myelin
What is Optic disc drusen?
• Calcified nodules within optic nerve head
0.34% - 2% of population
- Bilateral in 75%
• Unclear pathophysiology - ? Impaired ganglion cell axonal transport
- Buried in childhood, more prominent with age
• Symptoms
- Most Px asymptomatic
Optic disc drusen: Examination
• Visual field loss in 75 - 87%
- Enlarged blind spot / arcuate defect
- Remains stable or very slowly progresses
• RAPD
- Possible RAPD if monocular/asymmetric
Optic disc drusen: Optic disc
• Appears small in diameter
• Anomalous vascular branching patterns
• Round, whitish, yellow refractile bodies
• Disc may be pale due to RNFL loss
Buried drusen vs swollen disc:
• Both may elevate the disc and blur its margins
• Optic disc drusen:
- Lack of hyperaemia
- Lack of microvascular changes
- Normal / atrophic nerve fibre layer
- Anomalous retinal vascular patterns
B-scan
Fluorescein angiography
MRI
Tilted optic disc:
• Oblique insertion of optic nerve
• Congenital or associated with myopia
• 1-2% of the population
- 80% bilateral
• Symptoms
- Asymptomatic
Tilted optic disc: Disc
• Oval, tilted appearance
• Inferior peripapillary atrophy
What to record when recording posterior pole?
• Write which eye
• Vitreous: clear or floaters if present
• Disc: see other slides
• Macula: healthy, comment on pigment if older and abnormalities if present
• Blood vessels:
-pathways and crossings normal
- A:V (measure after 3 anastomoses),
• Periphery: healthy, flat, comment on pigment and abnormalities if present
Tilted optic disc: Visual field
• Bitemporal loss
• Superior arcuate scotoma
Define optic neuropathy:
• Neuropathy = disease or dysfunction of one or more peripheral nerves
• Damage to the optic nerve due to any cause
• Both swelling and atrophy give signs of optic neuropathy
optic neuropathy: General symptoms
• Reduced vision
• Colour vision (possibly on probing)
Time course rules of thumb for optic neuropathies:
• Minutes: ischaemic retinal event
• Hours: most commonly ischaemic, more likely optic nerve
• Days-weeks: more frequently inflammation (may reflect ischaemia)
• Months-years: compressive
• Could be overlap
optic neuropathy: Examinations done
• Best corrected visual acuity
• Pupillary testing
• Fundus examination
• Visual field testing
• Colour vision
• Contrast sensitivity
optic neuropathy: General signs
• VA reduced
• Pupils : RAPD if unilateral/asymmetric
• Fundus exam: Optic disc abnormal or normal
• Visual fields: visual field loss
- Paracentral scotomas, central scotomas
- Arcuate scotomas, broad + nasa defect
- Nasal radiating fibres, temporal wedge
- Blind spot enlargement
Optic neuropathy: Colour vision
• Optic neuropathies manifest red-green defects
• Red desaturation, “maroon”
• Optic nerve: dyschromatopsia > visual acuity loss
• Macula: dyschromatopsia = visual acuity loss
• Persisting defect even after visual recovery
Optic Atrophy: describe
• Pale (chalky white) disc appearance with sharp margins
• Damage to retinal ganglion cells at any level
• Lesion in optic pathway anterior to lateral geniculate body
- Anterior to chiasm - unilateral;
- Posterior to chiasm - bilateral
• 4-6 weeks to appear from time of axonal damage
Optic Atrophy: Primary vs secondary
• Primary Optic Atrophy
No adjacent swelling of ON head
• Secondary Optic Atrophy
Preceded by swelling of ON head
Optic Atrophy: Primary Causes;
• Retrobulbar neuritis (inflammation, infection or demyelination affecting optic nerve behind optic disc)
• Compression by tumour or aneurysm
• Hereditary optic neuropathies
• Toxic and nutritional optic neuropathy
Optic disc oedema: Describe
• Swelling of nonmyelinated nerve fires from impaired axoplasmic
- Evidence of acute/evolving pathology
Optic disc oedema: Signs
• Elevated appearance of nerve head
• Filling of cup
• Retinal vessels drape over disc margin
• Blurring of margin
• RNFL oedema - greyish appearance that obscures vessels
• Hyperaemia
• Retinal venous dilatation & tortuosity
• Peripapillary haemorrhages, exudates, cotton wool spots
Optic disc oedema: Most common causes;
• Papilloedema
• Anterior Ischaemic Optic Neuropathy
- Arteritic anterior ischaemic optic neuropathy (AION)
- Non-Arteritic Anterior Ischaemic optic neuropathy (NAION)
• Inflammation / Optic Neuritis (demyelinating, infectious, non-infectious)
Optic disc oedema: Papilloedema
Describe
• Raised intracranial pressure
• Pressure is transmitted to the optic nerve
• Swelling of the nerve head results
• BILATERAL
Optic disc oedema: Papilloedema
GH Symptoms
• Occasionally asymptomatic (could be picked up in routine eye exam)
• Nausea and vomiting
• Deterioration of consciousness
• Pulsatile tinnitus
• Headaches
Optic disc oedema: Papilloedema
Symptoms: headaches
• Can be ‘muzzy headed’ at start, develops into extreme pain, usually presenting at hospital within 6 weeks
• Characteristically in morning, waking up px
• Generalised or localised
• Worse when pressure increases: moving head, bending over, coughing
• Very rarely, headache absent
Optic disc oedema: Papilloedema
Symptoms : Ocular
• Visual symptoms often absent but reduced VA in later stages
• Transient visual loss
• Horizontal diplopia (6th nerve palsy)
• Constriction of visual field
• Altered colour perception
Optic disc oedema: Papilloedema
Management
• Community Optometrist: same day referral to hospital eye service
• In hospital eye service: Treatment of cause
Anterior Ischaemic Optic Neuropathy (AION): Describe
• Most common optic neuropathy over 50 year olds
• Represents ischaemic damage to optic nerve head
What are the different types of AAION?
• AAION
• NAION
Arteritic Anterior Ischaemic Optic Neuropathy (AAION): Describe
• 5-10% of AION cases
• Occurs in older patients
• Caused by Giant Cell Arteritis (GCA)
- Inflammatory and thrombotic occlusion of short posterior ciliary arteries causing optic nerve head infarction
Arteritic Anterior Ischaemic Optic Neuropathy (AAION): Systemic Symptoms
• Usually 60-80years old
• Tender, hardened, non pulsatile temporal artery Scalp tenderness, especially on brushing hair
• Jaw claudication (pain on speaking or chewing, almost pathognomonic)
• Proximal muscle weakness (typically shoulders)
These may cause:
• Reduced appetite
• Unexplained weight loss
• Unexplained lethargy, malaise, depression
Arteritic Anterior Ischaemic Optic Neuropathy (AAION): Visual symptoms
• Sudden, profound, visual loss
• Usually unilateral (initially)
• May be proceeded by transient visual obsurcations, flashing lights
• Periocular pain
Arteritic Anterior Ischaemic Optic Neuropathy (AAION): Visual examination
• VA very poor
• Pale swollen disc
• Cotton wool spots (signifying retinal ischaemia)
• Over 1-2 months, swelling resolves leaving optic atrophy
Non-Arteritic Anterior Ischaemic Optic Neuropathy (NAION): Describe
• 90% of AION cases
• Occlusion of short posterior ciliary arteries causing infarction of optic nerve head
• Typically in 55-70yrs (average 60yrs)
- younger compared to AAION
Non-Arteritic Anterior Ischaemic Optic Neuropathy (NAION): Risk factors
• Structural “crowding” of the disc when cup is small/absent
Common modifiable risk factors include:
• diabetes
• hypertension
• high cholesterol
• smoking
Non-Arteritic Anterior Ischaemic Optic Neuropathy (NAION): Symptoms
• Sudden, painless loss of vision
• Unilateral
Non-Arteritic Anterior Ischaemic Optic Neuropathy (NAION): Examination
• VA
- Moderate to severe reduction in VA in most px
- Most px have no further visual loss although in a small number, visual loss continues for about 6 weeks
• Visual fields
- Commonly inferior altitudinal defect
• Dyschromatopsia
- Proportional to amount of VA loss
Non-Arteritic Anterior Ischaemic Optic Neuropathy (NAION): Fundus exam
• Disc oedema diffuse or segmental
• Disc hyperaemic with abnormal appearance of blood vessels on surface
• Often few peripapillary flame-shaped haemorrhages
• Atrophy within 3 to 8 weeks of onset
• Contralateral eye usually small with absent cup; “disc at risk”
Anterior ischaemic Optic Neuropathy (AION): management
• Community: immediate (same day) referral to ophthalmologist
• Treatment aimed at preventing blindness of 2nd eye
Optic neuritis: causes
• Infection of the optic nerve
- Caused by local infection e.g. sinus
- Following a viral infection e.g. chicken pox
- Following an immunisation
• Inflammation of the optic nerve (non-infectious)
- Sarcoid
- Autoimmune
• Demyelination of the optic nerve (most common)
Optic neuritis: demylination
• Demyelination disrupts nerve conduction within brain, brainstem and spinal chord sparing peripheral nerves
• Common causes:
- Multiple sclerosis (most common)
- Isolated optic neuritis with no other demyelination, but that may subsequently develop
Multiple sclerosis: describe, + relationship to optic neuritis
• MS is an inflammatory, demyelinating disease of the central nervous system (CNS)
• Multiple exacerbations characterised by variable CNS involvement
• Exacerbations are separated in time and anatomical location
• Optic neuritis is the presenting feature in15-20% of those with MS
• 50% of those with MS will get optic neuritis at some point
• If got optic neuritis, the overall 10 year risk of getting MS is 38%
Optic neuritis: symptoms
(reminder: optic neuritis is an infection, inflammation or demyelination of the optic nerve)
• Monocular visual impairment
• Subacute: develops over several days to 2 weeks
• Discomfort, exacerbated by eye movements which precedes visual loss in majority of cases
• Globe tenderness
Optic neuritis: examination
• VA 6/18-6/60 (or worse)
• RAPD
• Reduced colour vison / red desaturation
• Reduced contrast sensitivity
• Field defects
• Generalised depression
• Nerve fibre bundle defects
• Central loss
Optic neuritis: Fundus examination
• Normal in most cases (retrobulbar neuritis)
• Could get swollen disc
Optic neuritis: Demyelination
If due to demyelination, may also get:
• cranial nerve palzies
• gaze palsies
•facial nerve palsies
• nystagmus
Optic disc oedema: management
• Difficult for high street practitioner to determine cause
• Due to possible causes, same day (emergency) referral to hospital is likely
