# Augmented Reality in Surgery: A Scoping Review
## 5 Discussion  
Augmented reality is an innovative technology that presents several advantages, with new applications still in development. Knowing about this technology is every day becoming more important and can provide information to medical doctors and encourage new applications and deeper research. The reason for its increasing success is connected to the possibility it offers to visualize and interact with digital objects without having to lose view of the real world to watch the monitor displaying the medical imaging of the area of interest [1]. Moreover, research has shown its capacity to reduce the exposure to ionizing radiation. This aspect is important because it is well known that ionizing radiations can have harmful effects with possible effects on biomolecules such as DNA, lipids, proteins, and cancer risks [87; 88; 89]. One study [71] calculated the average of the staff radiation exposure using AR that, compared to the literature values, decreased to less than 0.01%. Moreover,the absorbed dose of the patient exposition resulted in a decrease of its value up to 32% compared to the quantities due to conventional techniques [71]. All these aspects may allow the diffusion of AR and the possibility of assuming it as a systemic tool in medicine. The analysis of the studies considered showed that AR finds applications in many surgery domains and especially in the field of maxillofacial surgery, orthopedics and oncology. In particular, oncology is one of the areas of application particularly indicated. In this sense, AR finds a lot of applications in different kinds of cancer with the aim of facilitating and reducing the consequences of the treatment as well as improving outcomes [14, 53, 54, 55, 56, 57, 58]. Even with regard to orthopedics, the use of AR can be particularly recommended and is aimed at promoting the quality of surgical interventions, and therefore improving the outcomes as well as reducing the risk of complications [64, 65, 66, 67]. In this sense, spinal surgeries represent an important area of application of AR where it can represent an important resource available to surgeons [68, 69]. Regarding the available display technology, the results obtained show that the Optical Viewer by Microsoft, HoloLens, is the most used [36, 39, 90]. The marker-based method paired with the rigid registration was the most used solution in the context of AR tracking and registration methods [42, 43, 44, 45, 46]. In this regard, it is clear that the goal is to be able to reduce or eliminate the problems associated with tissue deformations. Unfortunately, the limited number of data available did not allow for more in-depth analyses on this issue. AR is a technology that is every day becoming more popular. Here we provided an idea of what it is, which technologies it is formed from and in which applications it is more popularly used. Unfortunately, some limitations still affect the application of AR in the surgical field. From our study, we noticed that the output is too much related to the accuracy of the registration and tracking systems that need to be as reliable as possible. Errors during those mentioned phases could lead to a misalignment of the VOs with the real world [91, 92]. Mainly for the HMDs, the different field of view between human vision and visors represents an obstacle too [93, 94]. Finally, one of the biggest issues that affects this technology is the vergence-accommodation conflict. In nature, the point where the eyes verge and focus is the same, while AR displays are featured by a fixed focal distance; consequently, the points of vergence and focus may be different. This causes discomfort, fatigue and different eye depth perception [95, 96, 97]. Some limitations characterize this study since the purpose of the review consisted in providing a contemporary view, but the results may exclude longitudinal trends. A potential problem in this study may also be the possible underrepresentation of documents about AR in surgery.