Toxic and Nutritional Optic Neuropathy

Excerpt

Toxic and nutritional optic neuropathies both present clinically with symmetric progressive bilateral vision loss, decreased color vision, central or cecocentral scotomas on formal visual field testing, and no relative afferent pupillary defect because of the symmetric nature of optic nerve involvement.

In most cases, vision loss progresses over months rather than days to weeks, and vision decreases slowly. A thorough history is crucial to making a diagnosis. Specifically, exposure to drugs, alcohol and tobacco use, dietary intake, and occupational background should be investigated in any patient presenting with bilateral symmetric slow visual loss.

Early in the disease, optic nerves usually appear normal or, on occasion, slightly hyperemic. Continued exposure to a toxic substance or nutrient deficiency would cause the slow appearance of bilateral temporal optic disc pallor due to the injury of ganglion cell axons, specifically in the papillomacular nerve fiber bundle. This would eventually lead to the diffuse pallor of the optic disc. If an obvious visual field defect is not shown on routine 30-2 perimetry, central 10-2 perimetry will demonstrate central or cecocentral scotomas.