Light-based method for the endovascular treatment of pathologically altered blood vessels

A method of applying light energy from a light emitting unit to a blood vessel, from within the vessel, the method comprising the steps of:

• introducing into the vessel a device comprising a light applicator and a catheter via which the light applicator is inserted into and guided within a blood vessel, wherein the catheter is closed at a distal portion of the catheter, wherein the catheter and the light applicator are arranged and adapted such that in use at any time the light applicator does not make intraluminal contact with any vessel wall and the light applicator is capable of delivering light energy through the sheath of the catheter;
• and
• applying energy to the vessel until the vessel is damaged and the vessel shrinks or collapses after removal of the catheter.