Optic Nerve Head Drusen
Drusen of the ONH are calcific bodies embedded within the parenchyma of the optic nerve. Evidence suggests that abnormal axonal metabolism leads to mitochondrial calcification and drusen formation. They are usually bilateral and associated with small, crowded ONHs with abnormal vasculature. When superficial, drusen appear on the optic disc as refractile, rounded pale-yellow or white deposits. Deeper ones may be mistaken for papilledema (pseudopapilledema). ONH drusen may cause visual field defects; in rare cases, they can cause an anterior ischemic optic neuropathy, resulting in significant vision loss. Most ONH drusen are located anterior to the lamina cribrosa and posterior to Bruch membrane (lamina choroidalis portion of the intraocular optic nerve).
Figure 15-9 Optic nerve atrophy. A, Gross appearance of an optic nerve (asterisk) with widened subdural space (arrow) due to shrinkage of the nerve.B, Low-magnification photo-micrograph also shows a widened subdural space (asterisks).C, Cross section of an atrophic nerve shows loss of axons (arrowheads), accompanied by glial proliferation and widening of fibrovascular pial septa (arrows).D, Glaucomatous optic atrophy. Masson trichrome stains the collagen of the sclera, lamina cribrosa, and meninges dark blue and the axonal fascicles pink. The optic nerve demonstrates advanced cupping (red arrow), accompanied by posterior bowing of the lamina cribrosa (arrowheads). Axonal atrophy and thickening of pial septa are present. The subdural and subarachnoid spaces are widened owing to severe optic nerve atrophy (double-ended arrow). A = arachnoid sheath; CRA = central retinal artery; D = dural sheath; P = pia.
(Part A courtesy of Debra J. Shetlar, MD; parts C and D courtesy of Tatyana Milman, MD.)
Figure 15-10 Schnabel cavernous optic atrophy. A, Photomicrograph shows atrophy resulting in cystoid spaces (asterisk) within the optic nerve. B, Photomicrograph shows cystoid spaces filled with alcian blue–positive material.
(Courtesy of Hans E. Grossniklaus, MD.)
Figure 15-11 Histologically, optic nerve head (ONH) drusen appear as discrete basophilic calcified deposits (arrows) just anterior to the lamina cribrosa (asterisk). The clear spaces in the ONH are histologic sectioning artifacts due to dropout of hard calcific material.
ONH drusen can be associated with the following:
However, they are more commonly seen in otherwise normal eyes. Occasionally, they are dominantly inherited.
Histologically, ONH drusen appear as basophilic, irregular, calcified acellular deposits (Fig 15-11) that contain mucopolysaccharides, amino acids, DNA, RNA, and iron. For more information, see BCSC Section 5, Neuro-Ophthalmology, and Section 6, Pediatric Ophthalmology and Strabismus.
Excerpted from BCSC 2020-2021 series: Section 4 - Ophthalmic Pathology and Intraocular Tumors. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.