Under certain conditions the blood flow in the ophthalmic artery can be reversed. This was proved radiologically and clinically in a patient suffering from a fistula of the cavernous sinus. The ophthalmic artery is an essential part of the circulus arteriosus. Ligature on the arteria temporalis superficialis has even positive results on the treatment of retinal ischaemia. From this, one can derive the conclusions for the theory of treatment of temporal arteritis.