OBJECTIVE: The pathogenesis of diabetic papillopathy largely is unknown, but case reports suggest that it may follow rapidly improved metabolic control. The present study was designed to investigate this hypothesis. DESIGN: Retrospective case-control study. PARTICIPANTS: Two thousand sixty-six patients with type 1 diabetes. METHODS: Review of clinical, photographic, and clinical chemistry records from a large diabetology and ophthalmology unit between 2001 and 2008. MAIN OUTCOME MEASURES: Simultaneous, bilateral diabetic papillopathy. RESULTS: The mean follow-up was 4.9 years. During 10 020 patient-years of observation, bilateral diabetic papillopathy developed in 5 patients. During the year preceding this incident, all 5 patients had experienced a decrease in glycosylated hemoglobin A(1c) (HbA(1C)) at a maximum rate of -2.5 (mean) percentage points per quarter year, which was significantly different from the changes in HbA(1C) observed in the remainder of the study population (P