Optic disc swelling
 

The optic disc margin is blurred. There is hyperaemia with or without splinter haemorrhage(s). The venous pulsation is absent. Note: it is safer to state that  the patient has optic swelling rather than papilloedema unless you have evidence of raised intracranial pressure.  Sometimes you may encounter patients with indistinct optic disc  without disc swelling or haemorrhages. In such cases, consider pseudo-papilloedema as in patients with high hypermetropia. Look for: hypertensive changes in malignant hypertension  extensive haemorrhages in central retinal vein occlusion  examine the contralateral eye for similar changes. The presence of bilateral disc changes strongly suggests intracranial hypertension as the cause. The most common case seen in the examination is a young overweight woman with benign intracranial hypertension.  optic atrophy in the contralateral eye ie. Foster-Kennedy's syndrome which is classically caused by meningioma of the optic canal (in the eye with optic atrophy). However, in both examination and real life the most common cause is sequential ischaemic optic neuropathy.

Questions:

1. What are the causes of a indistinct optic disc margin?

Answer
Irregular optic disc can be caused by true disc oedema or pseudo-papilloedema.

True disc oedema

increased intracranial pressure
demyelination
inflammatory such as posterior uveitis of various causes
infectious such as toxoplasmosis, CMV retinitis, Lyme disease or HIV infection
vascular cases such as CRVO, malignant hypertension, 
diabetic papillopathy, anterior ischaemic optic neuropathy which may be arteritic or non-arteritic
orbital diseases and tumours such as dysthyroid eye disease, 
orbital cellulitis, metastatic lesions tumours and infiltrative diseases
of the optic nerve head for example metastatic disease, melanocytomas, optic nerve gliomas and meningiomas
Leber's optic neuropathy
toxic and nutritional optic neuropathies such as ethambutol, lead poisoning and chloramphenicol

Pseudopapilloedema

optic disc drusen
neovascularization
myelinated nerve fibers
high hypermetropia
nerve head tumours such as astrocystic hamartomas
Bergmeister's papillae
 

2. How can you differentiate between optic disc swelling resulting from papilloedema from that caused by optic nerve compression?

Answer
Physical signs: papilloedema typically shows bilateral disc swellings whereas optic nerve swelling is usually unilateral.
Visual acuity: the VA is normal in early papilloedema but reduced in optic nerve compression
Pupillary reaction to light: there is no relative afferent pupillary defect in papilloedema whereas in unilateral optic nerve compression the swollen eye exhibits relative afferent pupillary defect.
Colour vision: colour vision is reduced in optic nerve compression but normal in papilloedema
Visual field: in optic nerve compression there is central scotoma whereas in papilloedema the typical field defect is enlarged blind spot unless the cause of the raised intracranial hypertension is a tumour affecting the visual pathway.

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