Introduction
A common causes of secondary optic atrophy include:
- Chronic papilloedema
- AION
- Papillitis
- Compressive lesions
For papilloedema, ICP increase can be due to:
- Idiopathic or hypertension
- Space-occupying lesions
- Increase in CSF production
- Impairment in CSF absorption
- Increase in BV
- Skull deformities
- Elevated vitamin A levels
- Drugs or medications such as tetracyclines
For Pseudopapilloedema, there is an elevation of the optic nerve without true disc oedema. The differentiation between true and pseudo papilloedema is critical.
- Papilloedema presents with vision loss and neurological impairment
- Pseudo are relatively benign, and includes small crowded disc, tilted disc and disc drusen.
- Crowded discs are more common in individuals with hyperopia or shorter axial length
- Tilted discs are typically congenital or acquired, and associated with myopia or astigmatism that primarily affects the nasal
- Disc drusen occurs in globular, mostly calcified deposits within the body and is typically bilateral but can be asymmetrical
- Can lead to nerve fibre loss and VFD
NAAION and AAION can also be causes of optic nerve atrophy.
Compressive Cause:
- Caused by lesions in the anterior orbit such as optic sheath meningioma
- Usually located in the intraorbital space, but can also occur in the intracanalicular portion.
- Can lead to chronic optic disc oedema, and after the oedema, atrophy develops.
- Optociliary shunts seen in about 30% of cases after swelling resolves. These form from the occlusion of the CRV, and forms to instead provide venous circulation of the retina through the choroid.
Other causes include papillitis, neuroretinitis and retrobulbar neuritis.
Dead Giveaways
Papilloedema
Due to elevated intracranial pressure, differentiating papilloedema from other swollen discs
Chronicity can lead to axonal damage and subsequent atrophy after resolution.
Grading:
Grade 0: Prominence of RNFL at nasal, superior, inferior poles. RNFL layer striations without tortuosity
Grade 1: C-shaped halo that is subtle and gray with a temporal gap, obscuring retinal details. Disruption of normal radial RNFL
Grade 2: Circumferential halo, elevation of nasal borders, no major vessel obscuration
Grade 3: Obscuration of >1 segment of major blood vessels leading disc. Circumferential halo, elevation of all borders, and halo with outer fringe irregularities.
Grade 4: Total obscuration on disc of a segment of major blood vessel. Elevation of whole nerve head, and cup. Border is completely obscured
Grade 5: All vessels are obscured
From Moran CORE
RNFL Analysis
Displays a very characteristic rainbow fringe pattern on RNFL analysis
Rainbow fringes Another classic feature is the thickening of the optic nerve head on OCT
Very thick, and will appear white on RNFL analysis. Bruch's membrane also displaces anteriorly sometimes. Fundus Autofluorescence
Can also be very helpful in diagnosis
Surrounding area of hypo-FAF due to the halo and swelling which obstructs transmission.
Small Crowded Disc:
Characterised by the criteria of <2.5DD distance between macula and optic head.
Can have complications if clotting occurs
Tilted Optic Disc:
The tilting of the optic disc will cause vessels to appear to shoot out of the disc rather than arc out
Additionally, will take on a progressive oval appearance, with two halo on either side of the oval representing the displaced rim
Note the vessels shooting out inferiorly, but curving upwards superiorly. There is an oval shape
Optic Nerve Drusen:
Superficial:
Very obvious by the globular deposits present in both FAF and normal photograph.
OCT reveals hypo-reflective spaces surrounding by hyper-reflective walls.
Features revealed as above Another defining feature is from the B-scan ultrasound
Note the surround hyper-reflectivity on ultrasound
Deep
The deep drusen are harder to identify, as it won't be present on fundus photography or red free.
Still visible on B-scan ultrasound
Papillitis:
Characterised by inflammation and deterioration of the optic disc.
Leads to dyschromatopsia, and usually experiences unilateral vision loss. Is usually rapidly progressive in history
Could be due to demyelinating diseases such as MS or encephalomyelitis, or due to viral/bacterial aetiology like polio, meningitis, measles. Can also be due to pernicious anemia, diabetes.
CAN be associated with GCA, and hence may need differentiation from AAION.
Presentation:
Rapid vision loss with fever, compared to papilloedema which has headaches in morning and vomiting, but vision is initially unaffected
Is usually unilateral compared to papilloedema's bilateral nature
Papillitis will display, like neuritis, desaturation with the red cap. Colour vision is spared in papilloedema
Pain on eye movement (neuritis), but not for papilloedema
RAPD present (neuritis), but can be manifest later on in papilloedema
No haemorrhaging unlike papilloedema
VF shows central/ceco-central scotomas. Papilloedema shows enlarged blind spot
diagnostic features
Features:
After resolution, it typically appears a dirty grey colour instead of chalky white in primary atrophy
Discs are no longer distinct
Lamina cribrosa also not visible due to filling of the cup by fibroglial tissue
Peripapillary sheathing of arteries, opto-ciliary shunts or folds can also be seen, depending on the underlying cause
RNFL loss corresponds to areas of discolour, along with significant constriction of visual fields.
Loss of physiological cup, sometimes haemorrhaging can be seen, distinct lifted appearance of rim, tortuous vessels
Papilloedema Symptoms:
Headache
Nausea
Vomiting
Loss of consciousness
Visual Symptoms (horizontal diplopia, transient visual disturbances)
Pulsatile tinnitus
Idiopathic Intracranial Hypertension by Modified Dandy Criteria
Symptoms and/or signs representing increased ICP or papilloedema
Documented high ICP
Normal CSF composition
Normal MRI contrast enhanced CT
No other cause of increased ICP
Compressive Cause:
Can have choroidal and retinal folds, as well as hyperemia and blurred disc edges.
Swelling does not always occur for ON sheath meningiomas, but if there is swelling, it indicates tumour is closer to the globe
Papillitis and Neuroretinitis
Papillitis can present with disc hyperaemia and oedema, and sometimes disc haemorrhages. Mst common optic neuritis seen in children
Neuroretinitis is characterised by disc swelling and macular involvement with macular star.
Retrobulbar is the most common optic neuritis, but is caused by demyelination, unlike the other two