Provided is a method that encompasses the determination of a virtual trajectory within a virtual representation of a patient's anatomy, wherein the trajectory is defined by a user's visual axis relative to the three-dimensional virtual representation of the patient's anatomy. The method includes acquiring image data which describes the three-dimensional virtual representation of the patient's body part, acquiring position data which describes a spatial position of a user's visual axis within a virtual-world co-ordinate system, determining visualization data based on the image data and the position data, and determining virtual-world trajectory data based on the position data.