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CHAPTER 2
State of the Art
2.1 Virtual Reality Exposure Therapy
It has now been almost 20 years that VR technologies have been experimented and evaluated
in order to treat phobias. The objective of VRET sessions is to desensitize the phobic
patient by exposing him/her to the anxiety provoking stimulus.
Many studies have been conducted regarding the use of VR in the treatment of phobias.
Traditionally, during in-vivo exposure, patients are asked to evaluate which 8 situations are
the most anxiety provoking for them. Then, they are gradually exposed to the fearful situations
and guided by the therapist. This is done in order to habituate the patient to the anxiety
provoking situation. In VRET, the same principle is used, but the patients are exposed to
computer generated scenes and scenarios instead of the in-vivo situation.
The first and most frequent type of phobia which has been tackled by VRET is acrophobia,
or the fear of heights. One of the pioneer studies using VRET was conducted by
Rothbaum et al. [Rothbaum et al., 1995]. They designed their environment using Wavefront
software (now belonging to Autodesk [Autodesk, 2009]) which they then integrated into a
VR application called The Simple Virtual Environment Library [Verlinden et al., 1993]. This
simple application allowed the loading of the scene composed of hierarchically grouped objects
and the creation of events for walkthroughs (e.g. pressing a key on the keyboard to move
forward in the VE). They presented a case study in which a patient was gradually exposed to
increasingly anxiety provoking situations through a Head Mounted Display (HMD). Their
results indicated a significant habituation from the patient regarding both anxiety symptoms
and avoidance of anxiety provoking situations. A second study was conducted by Hodges et
al. using the same software and hardware [Hodges et al., 1995]. They created three types of
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