The Ischemic Optic Neuropathy Decompression Trial (IONDT) was a randomized clinical trial designed to compare the improvements in visual acuity at 6 months in patients assigned to receive surgery with optic nerve sheath decompression with those assigned to careful followup. A cohort of patients, with a baseline visual acuity of better than 20/64 are also being followed to better understand the natural history of the disease, including second eye involvement.