An optical method and apparatus is utilized to evaluate the presence of tissue modification, in particular, to evaluate tissue ablation using light scattering spectroscopy realized via optical fiber(s). Such a technique allows for detection of the presence of tissue modification and provides depth information, such as, for example, depth of an ablated lesion. The method and apparatus as described herein can be used for in- vivo, real-time monitoring during predetermined procedures, such as, cardiac tissue ablation for therapeutic reasons.