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