While on the one hand, glaucoma patients have reduced OBF and this OBF reduction even has a predictive power for the progression of GON [60], on the other hand, a blood flow reduction by artherosclerosis, multiple sclerosis or by a high level of endothelin-1 (e.g., multiple sclerosis), do not increase the risk for GON significantly. This evidence concerns the gene EDN1 and multiple sclerosis.