OBJECTIVE: 1) To evaluate the management of acute isolated optic neuritis (ON) by ophthalmologists and neurologists; 2) to evaluate the impact of clinical trials; 3) to compare these practices among 7 countries. METHODS: A survey on diagnosis and treatment of acute isolated ON was sent to 5,443 neurologists and 6,099 ophthalmologists in the southeast-USA, Canada, Australia/New Zealand, Denmark, France, and Thailand. USA data were compared to those of other countries. RESULTS: We collected 3,142 surveys (1,449 neurologists/1,693 ophthalmologists) (29.8% response rate). In all countries, ON patients more frequently presented to ophthalmologists, and were subsequently referred to neurologists or subspecialists. Evaluation and management of ON varied among countries, mostly because of variations in healthcare systems, imaging access, and local guidelines. A brain MRI was obtained for 70-80% of ON patients; lumbar punctures were obtained mostly in Europe and Thailand. Although most patients received acute treatment with intravenous steroids, between 14% and 65% of neurologists and ophthalmologists still recommended oral prednisone (1 mg/kg/day) for the treatment of acute isolated ON. In all countries, steroids were often prescribed to improve visual outcome or to decrease the long-term risk of multiple sclerosis. INTERPRETATION: Although recent clinical trials have changed the management of acute ON around the world, many neurologists and ophthalmologists do not evaluate and treat acute ON patients according to the best evidence from clinical research. This confirms that evaluation of the impact of major clinical trials ("translational T2 clinical research") is essential when assessing the effects of interventions designed to improve quality of care.