The present invention relates to a catheter and a corresponding method to use a catheter, wherein the catheter provides for two inflatable balloon devices which are configured to perform a relative movement with respect to each other. By uncovering an opening upon distancing the two inflated balloon devices, a confined and spatially separated vessel section is created in which optical energy may be emitted to treat the vessel. The presented catheter advantageously enables the user to generate micro foam for sclerosing application inside the catheter.
