Optic disc drusen

Optic disc drusen are primarily asymptomatic and a case of accidental finding during an eye examination. Approximately 9% of patients may present with visual obscurations.(5)

The optic disc drusen can be superficial, and in such cases, they give a “lumpy-bumpy” clinical appearance, or they can be located deeper within the optic nerve.

There are typical signs which should raise suspicion of optic disc drusen:

• Elevated, often small, optic disc with indistinct and irregular disc margins.
• Drusen are seen as round, white/yellow refractile bodies on the surface of the nerve or buried beneath it.
• Anomalous vascular branching pattern (tortuosity, optociliary shunt vessels).
• The nasal margin is the most common site of drusen.
• Spontaneous venous pulsations.
• The afferent pupillary defect if there is asymmetric nerve involvement.

The optic drusen can also cause visual-field defects. Those defects can be present in childhood and slowly progress over time.(6) There are two primary defects found in the optic disc drusen:

• An arcuate defect in the inferonasal quadrant, secondary to direct compression or displacement of retinal nerve fibre layers by drusen.(7)
• An enlarged blind spot due to pseudopapilloedema or leakage from the blood vessels.(8)

The visual defects are more often present in patients with superficial drusen.

Slit lamp examination and colour fundus photography – superficial drusen are easily seen as lumps on the surface of the optic disc.

Fundus autofluorescence (FAF) – the optic disc drusen are highly auto-fluorescent, and FAF imaging is an excellent and helpful tool to recognise them. The imaging modality is used for the superficial optic disc drusen.

Ultrasound is a great technique to recognise the buried (deeply located) optic disc drusen. It depends on the percentage of calcium within the drusen.

Optical coherence tomography provides the ability to detect optic disc drusen to the lamina cribrosa. It is an excellent tool to recognise and distinguish superficial from deep drusen.

Due to its location, the optic disc drusen may cause associated retinal changes, including retinal vasculature changes. Patients may present with tortuous retinal vasculature, vascular loops and/or optocilliary shunts. There are described case reports where patients developed central retinal artery occlusion (CRAO) and central retinal vein occlusion (CRVO) secondary to optic disc drusen. Uncommonly, patients with optic disc drusen can develop peripapillary choroidal neovascularisation (CNV), intraretinal flame-shaped haemorrhage, deep optic disc haemorrhage, or vitreous haemorrhage (rarely).(9,10)

The appearance of optic disc drusen may lead to wrong suspicion of papilloedema, which is an urgent and potentially life-threatening condition. Therefore, it is essential to be familiar with specific clinical signs on distinguishing optic disc drusen-related pseudopapilloedema from the real swelling of the optic disc.

Table 1: Characteristics of papilloedema vs pseudopapilloedema

There is no treatment warranted for optic disc drusen. Generally, the prognosis is good, and you should monitor your patient regularly. The potential retinal complications (CRAO, CRVO, peripapillary CNV) should be treated as required.

In the case of the progression of visual-field loss, there is no agreement on treatment. Some experts propose IOP-lowering eye drops.(11) Patients with optic disc drusen may have co-existing glaucoma, and monitoring glaucoma progression in such patients is challenging. You should refer those patients to an ophthalmologist so that they can be monitored.