A phobia is a type of anxiety disorder, usually defined as a persistent fear of an object or situation in which the sufferer commits to great lengths in avoiding, typically disproportional to the actual danger posed, often being recognised as irrational. In the event the phobia cannot be avoided entirely the sufferer will endure the situation or object with marked distress and significant interference in social or occupational activities.
Some therapists use virtual reality or imagery exercise to desensitise patients to the feared entity. These are parts of systematic desensitisation therapy. We are creating a framework that enables the adaptation of the use of Augmented Reality for these therapies. Using a head mounted display device to which a camera is fixed the user can see the real world with virtual objects.
The user wearing the HMD moves in a completely safe area, and he/she is aware of that, but he sees the elements that may trigger the phobia. He/she tries to control the fear because he/she knows that those elements are completely virtual. An example is show below of a user walking near a well that may trigger acrophobia reactions.
Bellow you can watch the video stream seen by the user. Here he can see his own feet while walking close to the border of a well. The view is completely dependent of the user pose and the virtual well is drawn over the image captured by the camera. Spatial sound elements are also added, this increases even more the realism, giving a true sensation of the presence of the virtual elements.
 Bourne, Edmund J. (2011). The Anxiety & Phobia Workbook 5th ed.. New Harbinger Publications. pp. 50–51. ISBN 572244135.