Six patients with nonarteritic ischemic optic neuropathy experienced worsening of visual acuity and field loss during the six-week period after onset (range, three to six weeks), without apparent ophthalmoscopic changes. Thereafter, visual function remained unchanged. Various medications were used, but none prevented deterioration of visual function. Although not a widely recognized phenomenon, progression of visual deficit occurred in these patients in the early weeks after onset of ischemic optic neuropathy. © 1988.