Three concepts are important about this tool and must be taken into account when using it:

• the immersion,

• interaction,

• realism.

 

It is consequently on these notions that Virtual Reality Exposure Therapy (VRET) will also depend. The degree of immersion is linked to the interfaces used and the necessary and beneficial level of immersion varies according to its field of application (Stanney et al., 1998). For TERVs, the greater the immersion in virtual reality, the more valid and usable the results will be, which will make it possible to highlight the real influence of this type of exposure. The interfaces must inform the user of the evolution of the virtual world (sensory interfaces) and report to the computer the motor actions of the user in the virtual world (motor interfaces). This interaction must take place in real time, that is to say without the individual perceiving a time lag between his action on the Virtual Environment (VE) and the latter's sensory response. If a shift takes place, it could generate cybersickness (nausea, dizziness, vomiting ...) which would jeopardize the immersion of the participant. Finally, the degree of realism of the virtual system can be characterized by its degree of resemblance to reality . It is available in terms of: graphics, layout of the premises, tasks to be performed, interaction with the VE, requested sensory modalities, expected motor responses, quality of social interaction, etc. . Realism and its perception can also be influenced by the patient's emotional experience and lived experience. Realism is a very important point which will influence the quality of the immersion and participate in improving the interaction between man and machine and therefore the effectiveness of the therapy.

 

In 2018, there were more than 7 million virtual reality headsets sold worldwide, all brands combined (Sony, HTC, Oculus ...), they are accessible to all for an investment within the reach of the general public. The Human-Machine Interactions (HMI) parameters stated above are therefore more than ever to be taken into account for users of today and tomorrow. Increasingly, VEs for therapies should be made available to the public . Those who wish can therefore, from home and with their own equipment, practice therapy without being accompanied during the sessions. For certain software, the agreement of a therapist will however be necessary to access the environments. This direct opening to the public is a step forward which nevertheless raises some questions. Informing future users but also future therapists who will give their approval, of the proper use of these tools for VRET and of the specificities of these technologies now seems essential.