Are you familiar with a treatment for varicose veins which involves "tightening" the valves as opposed to closing the vessel?

Yes: There have been several attempts that have been made over the years to try and perfect a technique of "tightening" the valve, rather than closing the vein. None have been extremely successful and all, for the most part, have been abandoned. There are certain rare occasions when it is still done today (mostly outside the us but, for the most part, most think the better choice is closing the vessel.

Vein surgery: There is investigational work being done to essentially place a cuff around a vein to limit the ability to dilate. This will then prevent the nonfunctional valves to work properly and prevent vein reflux. Also work being done to suture the valves to tighten them. Most of this is done for deep vein problems, not varicose veins. Not sure any of this is really ready for "prime time".

Varicose Veins: There is some experimental type work done in this area, but there is no available effective treatment of valve "tightening" available today. The best available therapy for the valve condition is the "closure" treatment as you mentioned, which uses heat energy (laser or radiofrequency generated heat) or chemicals (sclerotherapy) to close the veins. Valve repair is not yet available.