Description
These are idiopathic, extracellular concretions within the optic nerve head, located anterior to the lamina cribosa. The condition is often bilateral, and is sometimes inherited in an autosomal dominant pattern. Drusen are thought to result from the accumulation of cellular debris and waste products, which may be accelerated in conditions including nerve fibre compression, scarring around the optic disc and optic atrophy. Optic disc drusen may cause clinical concern as they enlarge and cause disc swelling (‘pseudopapilloedema’), which may be mistakenly attributed to disc swelling resulting from raised intracranial pressure (‘true’ papilloedema).
Symptoms
Usually asymptomatic. Some patients with optic disc drusen describe occasional, transient visual obscurations, which may again invoke clinical suspicion of raised intracranial pressure. Sudden loss of vision or visual field defects may occur with the complications described below.
Signs
(a) The optic disc appears normal when drusen are present in small amounts beneath the surface of the optic disc. As they accumulate – often during adolescence – the nerve head becomes enlarged with lumpy, irregular margins; and the optic cup is progressively effaced. As the drusen reach the disc surface, they appear as small, waxy, yellow nodules. They often become calcified later in life.
(b) Some features that often help to differentiate optic disc drusen from papilledema include:
- Irregular disc margins or surface, with reduced or absent optic cup
- Vessels arising from the centre of the disc and dividing earlier than normal
- Asymmetry of disc topography between eyes
- The disc surface does not usually look inflamed or hyperemic. Hemorrhages, exudates and cotton-wool spots in the vicinity of the optic disc are typical in papilledema.
- Drusen show antofluorescence under blue light without fluorescein administration
(c) Vision loss: Typical visual field defects are gradual enlargement of the blind spot and inferonasal quadrant or arcuate nerve fibre bundle defects. Occasionally acute loss of vision of variable severity occurs due to subretinal exudation and hemorrhage resulting from drusen-associated new vessel formation. Rarely acute loss of vision may also occur when drusen impede the normal passage of fluid and metabolites through the optic disc, resulting in acute disc swelling, vascular occlusions or focal retinal ischemia
Incidence
Common (approximately 1 in 300).
Significance
May simulate papilledema and prompt unnecessary anxiety and investigations to exclude intracranial lesions. Occasionally causes visual field loss and reduced acuity.
Differential Diagnosis
Papilledema, Presumed Ocular Histoplasmosis Syndrome, Angioid Streaks, Sarcoidosis, Pseudotumour Cerebri, Optic Pit.
See Also
Choroidal Neovascularisation, Central Retinal Vein Occlusion, Branch Retinal Artery Occlusion
Management
There is no treatment for optic disc drusen.
Additional investigations
Computed tomography (CT) and ultrasound can detect calcification within buried drusen. Intravenous fluorescein angiography will show fluorescence of the drusen prior to any dye injection (‘autofluorescence’). Subsequent hyperfluorescence is well-demarcated and confined to the optic disc. These features are not observed in papilledema. Choroidal neovascularization is a rare complication. Visual field assessment
Prognosis and Review
Optic nerve drusen are usually stable. Complications occur occasionally from compression effects on the nerve fibers or blood vessels. Annual review may be indicated depending upon the extent of the lesion.
Figure 1.
Irregular disc margins; early-branching vessels; note absence of haemorrhages or exudates around the disc.
Figure 2.
Scanning laser tomography scan quantifying the raised surface shape.
Figure 3.
Computed tomography scan demonstrating optic disc calcification.