1-5,6 - Optic Neuropathy Flashcards
ONH coloboma
- What is it?
- Appearance?
- Cause?
Congenital.
A missing chunk of ONH.
- Appear as discrete glistening white “bowl-shape” excavation at ONH
- Typically infero-nasally (last place optic fissure closes)
- ONH may be enlarged
- Uni/bilateral
- Choroidal fissure incomplete closure. Usually sporadic, can be autosomal dominant PAX6 gene.
ONH pit
- What is it?
- Appearance?
- Symptoms?
Congenital.
Localised hole/cavity within the optic disc at birth. A small round/oval depression inside ONH.
- Temporal most of the time but can be centre
- Variable appearance
- Unilateral mostly
- VF is slightly affected although patient may not notice. Severity due to leading to maculopathy.
Potentially either:
- Vitreous cavity – Vitreous traction exerts –ve pressure and drives fluid movement
- CSF – Abnormal route of communication between ON and retina or sub-retinal space
- BVs – leakage
Complications can occur at any age.
Morning Glory Disc
- What is it?
- Appearance?
- Cause?
Congenital.
Depression of posterior side of the eye which just happens to have the ONH within it.
2)
- ONH is orange/pink and enlarged with funnel-shaped excavation
- Surrounding ring/annulus of hyper/hypopigmentation of choroid
- Overlying white glial tuff in centre
- Increase no. of BVs emerging radially
- “Macula capture” if macular is part of it
- Unilateral usually.
- Abnormal/missing formation of sclera and lamina cribrosa.
- Females. Associated w/ cerebrovascular anomalies. Can lead to exudative RD
Tilted disc syndrome
- What is it?
- Appearance/characteristics?
Congenital.
ON inserted at oblique angle rather than perpendicular to posterior of eye globe. ONH will appear tiled/obliquely positioned.
- Often happens infero-nasally.
- Situs Inversus (reverse vascular pattern where BVs go nasally before temporally)
- Sclera crescent.
- Nasal fundus ectasia (Part of eye that’s buldging). Under fundus imaging, brighter part of globe is buldging due to stretching.
- Tend to have myopia/astigmatism.
- Usually bilateral.
Optic Disc Hypoplasia
- What is it?
- Appearance/characteristics?
- Cause?
Congenital.
Decreased nerve axon number.
- Small ONH (less than 1.5mm which is abnormal) and pale
- Surrounding yellow-white ring. This is because optic nerve is small and doesn’t fit sclera canal.
- Uni or bilateral.
- Underdevelopment of ON during gestation. Likely environmental such as drug abuse or diabetes. Can be associated with CNS or pituitary gland abnormalities.
Note: Hypoplasia can be measured as Disc Diameters away from macula. If >4 DD, very likely hypoplasia.
Myelinated nerve fibres?
- What is it?
- Appearance/characteristics?
- Cause/association?
Congenital.
a.k.a. Optic Disc Medullation
Anterior to lamina cribrosa, fibres are myelinated
- White opaque feathery edges. Can run along arcuate pattern if diffuse enough.
- Share border with ONH
- Run along arcuate bundles
- Unilateral mostly
- Myelination can obscure BVs
- Larger blind spot
- Defects allow oligodendrocytes to continue myelination. Down syndrome, turner syndrome, and epilepsy. Usually sporadic.
ONH drusen?
- What is it?
- Appearance?
- Complications?
- How to examine it?
Congenital.
A.k.a. pseudopapilloedema
- Acellular calcified concretions anterior to lamina cribrosa (not same as retinal drusen). They are buried at childhood but more exposed with age.
- Refractile, white-yellow, crystalline deposites within ONH
- Bilateral mostly.
- Vascular complications such as nicking or compressing BVs like CRA or CRV.
- Fundus autoflourescence. Note that ONH drusen may look like papilloedema but just because it is drusen, doesn’t mean you can rule out oedema.
- CT shows small light at ONH
- OCT
- Ultrasound lights up as hyperreflective lesion.
Papilloedema
- What is it?
- How to measure value?
- Causes?
Acquired.
- Swelling at ONH exclusively secondary to raised ICP.
- Lumbar puncture/spinal tap.
ICP can be raised due to a multitude of causes
- Intracranial lesions
- Cerebral oedema
- Impariment of CSF absorption
Any increase in ICP will affect eye because it increases pressure at subarachnoid spaces which surround the optic nerve hindering anterograde axoplasmic flow within RGC axons.
Appearance of Papilloedema?
Early:
- Mild ONH hyperaemia (redder than usual)
- Optic cup preserved
- Indistinct ONH margins and peripapillary RNFL striations
Acute:
- Severe ONH hyperaemia (More red)
- Can’t see cup
- Larger ONH
- Vascular congestion (venous enlargement, peripapillary flame haemorrhages, cotton wool spots)
- Mechanical deformation (paton lines)
Severe:
- (Same) Severe red
- (Same) No cup
- (Same) Enlarged ONH
- (Same) Vascular congestion (engorgement of veins and optociliary shunts)
- Hard exudates (liquid part of CWS reabsorped)
Atrophic:
- Subsided swelling
- NRR pallor
- Narrowed arterioles
Pseudotumour cerebri
Idiopathic Intracranial Hypertension
- Raised ICP w/ no known cause.
Optic Neuritis
- What is it?
- 2 types?
- Presentation?
Group of inflammatory diseases against the myelination. Eventually, RGC apoptose.
Atypical
- Caused by another disease. Infection causes inflammation or autoimmune
Typical
- Disease is the demyelination. Isolatied neuritis or lesions.
Symptoms of visual loss, periocular pain, and CV defect. Unilateral typically.
- Most neuritis appears normal since inflammation behind globe (Retrobulbar neuritis).
- Inflammed/swollen ONH (Papillitis)
- Neuroretinitis when inflammation of RNFL causes macular star shape (lipids leak out of henle’s layer)
Retrobulbar Neuritis
- How to pick it up/diagnose it?
- VF may show enlarged blind spot
- MRI/CT shows enlarged optic nerve
Optic Neuritis:
- Most common reasons for it?
- Diagnose that how?
- Multiple Sclerosis. Chronic demyelination leaving areas of scarring.
- MRI shows Dawson’s Fingers
AION
- What is it?
- Two categories?
Anterior Ischaemic Optic Neuropathy. Short posterior ciliary arteries occuluded. Partial or total infarction of ONH.
- Arteritic and Non-arteriritc
Describe Arteritic AION
- What is it?
- Associated w/?
- Symptoms?
- Appearance?
- Emergency
- SPCAs inflammed so swollen so occuluded.
- Ocular manifestation of Giiant Cell Arteritis (GCA) is the systemic condition which causes A-AION
- Can eventually affect the eye at some point.
- Associated w/ Polymyalgia rheumatica
General symptoms:
- Fever
- Fatigue + malaise
- Weight loss
- Proximal muscle pain + stiffness
- Jaw claudication (cramp like jaw pain from chewing or talking too long, is exclusive to GCA).
Visual symptoms:
- Amaurosis Fugax – Fleeting vision every once in a while
- Unilateral vision loss
- Diplopia
- White, pale ONH, few hemorrhages, unilateral at start but can become bilateral.
