Table 1.

Overview of devices and features.

Tool (year)		Communication features	Visual features	Relevant studies
Commercial HMDsa
	Vuzix Wrap 920AR (2010)	Internet transmission of video data	Camera-captured video feed of mentor’s hand gestures is overlaid on mentee’s HMD, and vice versa	Chinthammit et al [31]
	Vuzix Wrap 1200DX (2013)	2-way audio-video communication over Wi-Fi	Camera-captured images of mentor’s hand gestures are transmitted to mentee’s HMD	Mather et al [32]
	Recon Jet (2013)	2-way audio communication over phone or Wi-Fi Integration with custom software for 1-way video feed to computer	Integration with custom Android-based triage app	Follmann et al [33]
	Google Glass (2013-2017)	Compatible with Google Hangouts for audio-video streaming on remote devices and 2-way audio communication	Projects SMS text messages from remote viewers into local user’s view Remote viewer moves a mouse cursor in local user’s view Remote viewer’s webcam captures image of their hands or tools that superimpose onto local user’s view	Broach et al [34] Ponce et al [35] Armstrong et al [36]
	Microsoft HoloLens (2016)	Compatible with Skype or other Windows applications for audio-video streaming on remote devices and 2-way audio communication	Displays instructions, patient data, and images Remote viewers annotate local user’s view and create 3D surgical trajectories on virtual limbs Displays hand gestures captured by sensor device used by remote mentor	Kaylor et al [37] Cofano et al [38] Liu et al [39] Hanna et al [40] Wang et al [41]
	Moverio BT-300 (2016) and Moverio BT-350 (2017)	Compatible with TeamViewer app for audio-video streaming on remote devices and 2-way audio communication	Remote viewers directly annotate local user’s view Remote viewers create and annotate screenshots to be displayed in local user’s view	Cofano et al [38]
	Vuzix Blade (2018)	Compatible with TeamViewer app for audio-video streaming on remote devices and 2-way audio communication	Remote viewers directly annotate local user’s view Remote viewers create and annotate screenshots to be displayed in the local user’s view	Cofano et al [38]
	Magic Leap One (2018)	2-way audio communication over Wi-Fi	Displays holographic patients and monitors that can be modulated by remote viewers	Hess et al [42]
	Microsoft HoloLens 2 (2019)	Compatible with Microsoft Teams for audio-video streaming on remote devices and 2-way audio communication	SMS texts messages from remote viewers projected onto local user’s view Display patient data and images Remote viewers directly annotate and blend pictures or videos into local user’s view 3D object annotation	Hill [43] Rigamonti et al [44] Martin et al [45] Van der Putten et al [46] Rafi et al [47] Bala et al [48] Mill et al [49]
Virtual presence tools
	Original augmented reality telementoring platform (2014)	Wired connection allows for the sharing of video feeds and audio communication	Image of mentor’s laparoscopic instruments is superimposed onto mentee’s monitor; hybrid video seen at both sites	Vera et al [50]
	Virtual interactive presence and augmented reality platform (2013)	2-way video streaming via internet Can combine with Skype or other teleconferencing software	Remote viewer’s hand or instrument is superimposed over local video feed Remote viewer can freeze screen or 2D annotate image using pen tool	Ponce et al [51] Ponce et al [35] Vyas et al [52] Davis et al [53]
	Help Lightning mobile app (2016)	2-way internet transmission of audio and video between phones	Foreground of physician’s video (eg, physician’s hand) is superimposed over patient’s video for live gesturing Physician annotates over patient’s live video	Ponce et al [54]
	Proximie (2016)	Audio-video streaming from local site can be accessed by remote computers via internet Viewers from different remote sites can access the same live stream and talk with each other and the local site	Virtual hand pointer or pen to mark video feed from local site Image of remote viewer’s hand is superimposed over video from local site Overlaying video with 2D images and 3D models Computer vision algorithm allows for the anchoring of annotations	Hassan et al [55] El-Asmar et al [56] Greenfield et al [57] Patel et al [58]
Other original systems
	System for Telementoring with Augmented Reality platform (2015)	2-way internet transmission of audio and video between tablets or to HMD	Remote viewer annotates over local site’s video Remote viewer places scalable instrument icons or labels over local site’s video Local user can access prerecorded video clips to guide procedure in the event that the remote connection is unstable [59]	Rojas-Muñoz et al [60-62] Andersen et al [59,63]
	Vuforia Chalk mobile app (2017)	2-way internet transmission of audio between devices Internet transmission of camera feed from local user to remote expert	Remote viewer annotates over local user’s live video Annotations remain anchored to objects in the video even if local camera moves	Ramsingh et al [64]
	Original tele-ultrasound system (2018)	Open-source software for communication between remote viewer and local user Internet transmission of ultrasound video and live video of local user’s environment sent to remote viewer’s laptop	Remote viewer draws or writes directly on ultrasound images being streamed by local user; hybrid video seen at both sites	Carbone et al [65]
	Augmented Reality–based Telerehabilitation System with Haptics (2019)	2-way internet transmission of audio and visual data via computers Haptic devices relay force feedback and motion to each other through networked computer	Camera data used to generate image of remote and local users sitting across from each other in a virtual space seen on 3D televisions	Borresen et al [66,67]
	Telestration with coaxial projective imaging (2022)	2-way audio-video streaming over the internet	Obtains images from local field that remote viewer can annotate System projects annotations onto local field directly	Zhang et al [68]
	Original remote training platform (2022)	2-way audio-video streaming over the internet	HMD optics has see-through transparency and enables display of instructional information and video	Stone et al [69]

^aHMD: head-mounted device.