An energy-based tissue-sealing system and method provide higher sealing quality by measuring and using optical feedback parameters that are directly correlated to structural changes of tissue. The tissue-sealing system includes a sealing energy source, an instrument having a mechanism for grasping and deforming the tissue and for delivering sealing energy to the tissue, a light source, optical sensors, and a controller for controlling parameters of the sealing energy generated by the sealing energy source based upon the optical parameters of the tissue structure sensed by the optical sensors. At the beginning of a sealing procedure, the controller may monitor an initial optical parameter of the tissue and select a target trajectory of tissue optical parameters based on the initial optical parameter. During the sealing procedure, the controller monitors at least one optical parameter of the tissue structure and controls at least one parameter of the sealing energy based on the at least one optical parameter.
