The use of Augmented Reality (AR) for the visualization of 3D biomedical image data is possible thanks to a growing number of hardware and software solutions. Significant efforts are made in the operating room or during surgery, where visual information of target structures can be either highlighted/added or dulled/removed. However, as technical challenges and barriers to development decrease, it is increasingly important to take into account the specific capacities and constraints of the surgeon's perceptual and cognitive systems. The talk will provide an overview of three aspects of surgical AR. First of all, the presentation of the basic concepts and definitions. Second, the presentation of current efforts to address legitimate problems in a surgical context, such as the accuracy of registration. Finally, a focus on visualization and its evaluation to improve the quality of the surgeon's perception. To illustrate these improvements, we focus on the example of partial nephrectomy, i.e. the partial removal of renal tissue in endoscopic image data.