Virtual reality
Around the same time, Douglas Engelbart used computer screens both as input and output devices. In 1968, Ivan Sutherland, with the help of many students including Bob Sproull, created what was widely considered to be the first head-mounted display (HMD) system for use in immersive simulation applications. It was primitive both in terms of user interface and realism, and the HMD to be worn by the user was so heavy that it had to be suspended from the ceiling. The graphics comprising the virtual environment were simple wire-frame model rooms. The formidable appearance of the device inspired its name, The Sword of Damocles.
Virtual reality cue reactivity
Arguably the most important facet in making a virtual environment seem real is an appeal to sight. A virtual reality headset, incorporating a head-mounted display (HMD) is placed in front of the eyes of a patient like a pair of sunglasses, enabling for complete visual attention. A virtual environment is then displayed. A system of motion sensors tracks movement of the patient's head. If the patient tilts, or turns his head to view another part of the room, the environment adjusts accordingly. This allows for a more realistic experience by limiting restrictions of the head.