When is it true optic disc edema?
The optic nerve head consists of a bundle of densely packed axons from 1.2 million retinal ganglion cells and also encases the central retinal artery and vein. Thus, true optic disc swelling should have both mechanical and vascular signs present. The above photo (Figure 1) illustrates a typical appearance of optic disc swelling.
Mechanical signs of swelling:
- Elevation of optic disc (best appreciated with stereoscopic view)
- Blurring of optic disc margins
- Filling-in of the optic cup
- Oedemaof peri-papillary nerve fibre
- Retinal and choroidal folds
Vascular signs of swelling:
- Disc hyperaemia
- Venous congestion
- Flamed-shape haemorrhages near the disc (peri-papillary haemorrhages)
- Exudates in the disc or peri-papillary area
- Cotton wool spots near the disc (nerve fibre layer infarction)
Papilloedema is the most important differential diagnosis in the presence of bilateral optic disc swelling. Therefore urgent neuroimaging is indicated.
- Defined as a bilateral, passive, non-inflammatory swelling of the optic disc secondary to raised intracranial pressure.
- Symptoms: transient obscuration of vision with normal pupillary reflexes.
- If permanent visual loss is present, or pupillary reflexes are abnormal; in the presence of optic disc edema, then other optic neuropathies should be considered, including: optic neuritis, ischaemic optic neuropathies and compression optic neuropathy.
- Stages of papilloedema:
- Early papilloedema – disc hypaeremia, disc elevation, dilation of retinal veins, flamed shape haemorrhages around the disc margins
- Established papilloedema – Signs from early papilloedema + obscuation of all borders of the disc, optic cup appears filled
- Chronic papilloedema – optic cup is obliterated, hard exudates at optic disc
- Atrophic papilloedema – optic atrophy