## 3 Discussion
However, we were unable to obtain clear, high-resolution surgical images because of the high illumination of the operating room and restricted location of markers. In addition, ensuring that instruments for AR-assisted surgery do not interfere with the functioning of the operator and assistant was also a huge obstacle. For this, a 4k camcorder was installed right under the astral lamp using a self-made cradle, and satisfactory images were obtained. This operation cannot be considered as a perfect AR-guided surgery, because it did not perfectly match the visual field of the operator. However, AR guidance was sufficient for reference at important points in the surgery, such as formulating the osteotomy lines. In particular, the osteotomy lines, which were shown in the form of a plane, were easily recognizable in terms of position and direction during the actual operation. It was also possible to refer to the locations where it was difficult to use surgical guides, such as the pterygomaxillary junction osteotomy line. Accuracy is extremely important in surgical operations using VR/AR devices. In several studies, optical systems have featured precision within 5 mm, which is considered an acceptable difference range for clinical application [20; 22; 23; 24]. [PERSON] et al. [25] reported an accuracy of 2.9 \(\pm\) 1.9 mm using a high-resolution magnetic resonance image for reconstruction and optimal tracking system. [PERSON] et al. [26] demonstrated a portable projection device with an accuracy of 1.3 mm. A few studies proposed that deviations of less than 2.7 mm could be accomplished using a head-mounted display [27; 28]. RGB camera and marker system is reported to have an accuracy of 1.9-4.9 mm [29]. In the present study, the operation was performed with an accuracy of 2.77 \(\pm\) 1.29 mm using an RGB camera and tracking marker system, which was within a reasonable range, similar to other established studies. To date, no clinical research has been conducted for maxillectomy using VR/AR aided surgical planning. Previously, maxillectomy and orbital reconstruction have been performed by computer-assisted surgery, including 3D printing guide or navigation system (Table 1). These surgeries involve additional costs for the fabrication of surgical guides and time-consuming procedures, such as registration and application of surgical guides. However, AR-guided surgery does not make the surgical guide and registration more convenient. The error in the present study was similar to that of previous studies. However, beginning with this report, AR/VR application in oral and maxillofacial surgeries will increase. Standard guides need a definite reference point, like the bone and teeth of patients, and more dissection is needed to locate a particular point. However, the AR guide used in this case had the advantage of requiring less incision and dissection. For AR-guided surgeries, all images must be restructured by a complex algorithm, with a high-performance computer [34]. Although AR accelerates the surgical procedure, preparing the entire system, including registration and calibration, might take up more time depending on the intricacy of the system [7]. Additionally, the AR guide and surrounding interfaces can interrupt the surgeon's field of vision and the surgeon can be distracted due to the increased information on the AR platform during operation [35]. Proper recognition of the 3D model and depth can also be a problem [7]. Excessive latency can reduce operation accuracy and lower the clinician's comfort; therefore, overall system latency should be considered. However, these drawbacks can be overcome with the enhancement of AR technology. Combination of VR and AR will allow for better results in surgical procedures. Compared to conventional computer-assisted surgery with a surgical guide, VR/AR assisted procedure is more economical and convenient for the surgeon. In this report, the accuracy of the AR guide was verified. However, the absolute accuracy of the AR guide could not be assured because only one case