Prior studies have shown that the vergence-accommodation conflict (VAC) negatively affects the interaction performance in Virtual Reality (VR) and Augmented Reality (AR) systems, particularly as object depth increases. This paper examines user selection performance across six different visual depths. Through a study closely resembling prior research, eighteen participants participated in an ISO 9241:411 task with six different depth distances. We observed that with higher depth values, selection times increased while the throughput performance of the participants decreased. Based on this finding, we propose a Fitts' law model based on the focal distances, which models pointing times in VR and AR systems with substantially higher accuracy. We hope that our findings aid developers in creating 3D user interfaces for VR and AR that offer better performance and an improved user experience.