We report optical reflectivity data of several representative high T c superconducting films before and after ion milling. A significant enhancement of optical reflectivity after ion milling of a few thousand Å is observed. We observed that features associated with a-axis texture vanished after ion milling, resulting in pure c-axis films. This suggests that a-axis grains reside mostly near the surface in post-annealed high Tc superconducting films. The fact that highly oriented c-axis films can be retained even after post-annealing (for raising Tc) may be important for practical applications.