The laser can only destroy the excess blood in the vessels that it can reach. Currently there is no laser that can reach all capillary vessels.

Additionally, some vessels have a very fast blood flow that the laser cannot reach. The current lasers only penetrate 1-2 mm. Capillaries (which make up a PWS/PWB0 vary in depth and size. You cannot target something that you cannot reach in depth, or catch in speed. However in some cases complete clinical clearance can occur.