In this randomized, placebo-controlled, double-blind clinical trial, 60 patients were assigned to receive either IVIg or a placebo over a period of 3 months. In order to be eligible, patients who meet the inclusion criteria needed to have a stable loss of visual function (unchanged between the pre-enrollment screening visit and the enrollment visit). All patients wre re-examined at 3, 6, 9, and 12 months, with the primary outcome being the impact of treatment on visual acuity at 6 months as determined by measurements on a retroilluminated Early Treatment Diabetic Retinopathy Study chart at 4 meters.