A 66-year-old man with a history of multiple myeloma presented with a superior scotoma in the left eye, jaw claudication, and arthralgias. A, A fundus examination revealed optic nerve edema, a small peripapillary hemorrhage, and a supratemporal cotton-wool spot. B, Visual field testing demonstrated a complete superior altitudinal defect. The patient subsequently underwent a left temporal artery biopsy, which revealed amyloid deposits within the arterial wall. C, A microscopic examination revealed marked infiltration of amorphous eosinophilic material within the tunica intima, tunica media, and tunica adventitia of the temporal artery (hematoxylin-eosin, original magnification ×40). D, Higher magnification demonstrates giant cells surrounding the eosinophilic deposits (hematoxylin-eosin, original magnification ×400). E, Staining of amyloid with Congo red produces characteristic birefringence under polarized light (original magnification ×40).