A method of and apparatus for processing optical coherence tomography (OCT) scans through a subject's skin (7), the method comprising: receiving at least one OCT scan through the subject's skin (7), each scan representing an OCT signal in a slice through the subject's skin； processing each OCT scan so as to determine the presence of at least one blood vessel (9) in each scan； determining a diameter of at least one of the at least one blood vessels (9) whose presence has been determined； and typically determining a depth profile of blood vessel density for different vessel diameters.
