Laboratory Studies
Laboratory studies are not usually necessary in the workup of patients with disc drusen.
In patients with suspected Leber hereditary optic neuropathy, mitochondrial mutations are helpful.
Imaging Studies
B-scan ultrasonography may be useful in identifying buried disc drusen. Because drusen are calcified, they demonstrate high reflectivity on ultrasound.
While rarely indicated, a CT scan may show small areas of calcification within the disc substance, which represent calcified disc drusen. Progressive field loss, dyschromatopsia, or visual acuity loss in patients with suspected buried disc drusen or visible disc drusen warrants consideration of neuro-imaging studies to rule out occult CNS lesions, in which case a CT scan carries the advantage of possibly detecting buried disc drusen.
Fluorescein angiography can be used to rule out true papilledema, which exhibits increased dilation of the peripapillary capillaries with late dye leakage. Disc drusen may autofluoresce on fluorescein angiography, which can be seen with red-free photo techniques, using the appropriate filters. [2] (Buried disc drusen may not autofluoresce.) In Leber hereditary optic neuropathy, disc leakage is not seen on fluorescein angiography.
After studying 68 eyes with optic nerve head drusen, Merchant et al concluded that enhanced depth imaging optical coherence tomography scanning detects lesions more often and better evaluates their shape and structure than conventional testing. [3] Lee et al also found that optic head nerve drusen shows a diverse range of findings on optical coherence tomography scanning based on age and disc size. [4]
Other Tests
Visual field tests should be considered, especially if optic nerve drusen are suspected. Constriction of the visual field can gradually occur; patients rarely have progressive field loss that is insidious or rapid.
Stereo color photographs of the optic discs are useful to document changes.
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Superficial optic nerve drusen. Note the irregular disc margins with preserved vascular and perivascular detail.