Commercially available head-mounted camera (ContourHD, Contour Inc.,Seattle, Washington, USA.). A: We wear the camera (white arrow) under a surgical cap. Because the device is cordless, video recording can be quickly and easily prepared. B: The equipment used in our study is shown. It comprises (clockwise): the head-mounted camera; 16GB microSD card; USB cable for transferring digital data to a computer; elastic headband camera mount.