There are a number of good options for how to best treat large veins on the hands, and yes, sclerotherapy is one good choice, although if the veins are truly large, they may require several treatment sessions. They can also be treated by endovenous laser, or by removal with minimally invasive phlebectomy, where they are taken out through tiny, needlestick holes. Another choice that works well in combination with these specific vein treatments, is to address the soft tissue volume loss often seen with aging, by adding dermal fillers to the back of the hand, such as Radiesse. I would recommend being seen by a specialist who has multiple treatment options available, who can determine which will work best for your needs.