Sarcoid optic neuropathy. a. Mild pallor of the left optic disc. b. The visual field of the right eye is normal (top) whereas the visual field of the left eye (bottom) shows diffuse depression that is worse in the nasal hemifield. c. Magnetic resonance imaging reveals abnormality of the left optic nerve, just anterior to the chiasm, that is irregular and enhances with gadolinium (arrow).