Optic atrophy is the end-stage result of insults to the retinal ganglion cells and their axons. Although the etiology varies, the downstream sequence of events leading to optic atrophy is uniform: injury to the retinal ganglion cells and the axons of the anterior optic nerve (the portion of the nerve near the globe) results in axonal swelling, clinically apparent as ONH edema (Fig 15-8). Axonal swelling and loss of retinal ganglion cells are followed by retrograde degeneration of axons (ie, ascending atrophy, or Wallerian degeneration) toward the lateral geniculate body. Pathologic processes within the cranial cavity or orbit result in descending atrophy toward the retinal ganglion cell bodies (see BCSC Section 5, Neuro-Ophthalmology, for more on optic atrophy). Loss of myelin and oligodendrocytes accompanies axonal degeneration. The optic nerve also shrinks, despite the proliferation of astrocytes and fibroconnective tissue (gliosis) in the pial septa (Fig 15-9).
Glaucoma is a group of diseases characterized by optic neuropathy, resulting in optic atrophy. Histologically, there is early loss of retinal ganglion cell axons, blood vessels, and glial cells, particularly at the level of the lamina cribrosa. As the disease advances, the ONH becomes excavated, with posterior bowing of the lamina cribrosa (see Fig 15-9D). Evidence of optic nerve atrophy may precede detectable functional vision loss. See BCSC Section 10, Glaucoma, for further discussion.
Figure 15-8 Optic nerve head edema. Swollen intralaminar axons demonstrate vacuolar alteration with pale staining (green arrows) and displace the retina laterally (green arrowhead) from its normal termination just above the end of Bruch membrane (black arrowhead). Juxtapapillary serous intraretinal fluid (black arrows) and serous subretinal fluid (asterisk) are also present.
(Courtesy of Tatyana Milman, MD.)
Another example of optic atrophy is Schnabel cavernous optic atrophy, which is characterized microscopically by large cystoid spaces in the nerve posterior to the lamina cribrosa (Fig 15-10A). These spaces contain mucopolysaccharides, which stain with alcian blue (Fig 15-10B). Although the condition was initially observed in glaucomatous eyes after acute intraocular pressure elevation, it has been increasingly identified in el derly patients without glaucoma who have generalized arteriosclerotic disease. The source of mucopolysaccharides was originally thought to be vitreous, forced into the ischemic necrosis–induced cavernous spaces by elevated intraocular pressure; however, the mucopolysaccharides are more likely produced in situ, within the atrophic spaces of the optic nerve.
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.