## 1 Introduction
Therefore, our system's usefulness should be considered to reduce cognitive load by annotation rather than the ability to draw precise lines on the endoscope image as a design consideration. However, according to [PERSON] et al. [14], it was questionable whether pointing operation by head movement could improve communication between operators. They found no significant difference in total operative time, the total number of instructions, and total time during which instructions were given with and without WHaSP, suggesting the need to consider improvement from multiple perspectives. To address these communication issues, the study by [PERSON] et al. [19] suggested that the use of pointing as the primary operation should be improved. They have conducted experiments on the selection and assembly of Lego bricks by remote collaborative work using two methods: a laser pointer visual assistance system (WACL) and a head-mounted display (HMD) with a line-drawing function. As a result, they concluded that the laser pointer instruction using WACL was beneficial enough to identify the work object and location. However, in situations where detailed explanations were required, the HMD with line-drawing input reduced the number of words and the user's work time giving instructions compared to the WACL, arguing for its effectiveness of line-drawing as a means of communication. This research was motivated by the desire to develop a prototype of a communication support system for endoscopic surgery with a line-drawing function operated by head movement. We adopted a Microsoft HoloLens, head-mounted Augmented Reality (AR) glasses that can be operated hands-free [2]. This device can detect the frontal direction based on the accelerometer and gyroscope sensors' information and projects a cursor on the surface of a real object in that direction. In our developed system, the cursor can be displayed on the surface of the screen where the endoscope image is projected in the operating room. The AR glasses wearer can then manipulate the cursor by moving the position of his or her head. The cursor plays the same role as the mouse cursor in computer operation, except that head movements manipulate the cursor. The system also allows a voice input to change line color and line thickness as well as start/stop commands for their convenience. In this way, the surgeon can give the other surgeon detailed positioning instructions for the affected area on the screen by moving the cursor with head movements. In order to determine the effectiveness of this prototype in an endoscopic surgery environment, it is necessary to check whether the performance of the proposed environment can be applied to the current HCI model of drawing operations. If this validation of model applicability can be achieved, this study can provide a contribution to the design of CSCW environments for endoscopic surgery. [PERSON] et al. [20] reported on a study that used Fitts' law to evaluate the performance of pointing operations using head movements. They evaluated the performance of two-dimensional discrete pointing operations by head movements using a sighting device attached to a helmet. As a result, the performance of pointing in 45, 135, 225, and 315 degrees was lower than that in horizontal and vertical directions using head movements. These results indicate that the direction of drawing by head movement affects the performance of pointing operations. On the other hand, as far as we know, no studies have evaluated the performance of drawing operations using head movements, and their characteristics have not been clarified. Since it is not a pointing operation but a drawing operation, we used the steering law [21], which is a derivative of Fitts' law and is used to evaluate the operability of drawing. By investigating the applicability of the steering law to drawing operations by head movement, it is verifiable as to whether or not the performance of drawing operations by head movement is affected by the direction of the operation.