Acrophobia patients are characterised by a persistent fear to stimuli which evoke a sense of height. These people constantly try to avoid such kinds of experience because they know their fear is excessive to the extent that it interferes with their normal life. Classical therapy consists in a graded exposure, as Drs. Schuemie explained, meaning that the patient is being exposed to a hierarchy of feared stimuli. Currently, there are three possible variants in treatment which are exposure to imaginary stimuli, in vivo exposure, and exposure in Virtual Reality.
The Dutch research team decided to test Virtual Reality treatment because it is safer and cheaper. Compared to the imaginary or in vivo therapy, there are more situations available in Virtual Reality with a greater control and a larger degree of privacy for the patient. Drs. Schuemie briefly mentioned the previous research in this area. In 1994, a team in Atlanta, Georgia, started to experiment with a glass elevator to cure acrophobia and fear of flying. The results were encouraging and the testing is still going on. At the University of Washington in Seattle, fear of spiders is successfully treated by generating scary situations in virtual environments.
The students in Delft have set up their own pilot study in collaboration with the Faculty of Psychology at the University of Amsterdam. It was their first experience with Virtual Reality and the original equipment was cheap. The patients were invited to wear stereoscopic VIO I-glasses with three degrees of freedom. A piece of cloth was utilised to shield the test persons from the real world. The virtual environment was protected by a railing and a grid. The hardware was kept simple, consisting of a Pentium Pro 133 Mhz.. The used software comprised a high level VR toolkit, known as superscape VRT 5.0.
Initially, three Virtual Worlds were built and the tested patients were invited to fill in a questionnaire consisting of two parts, assessing their exposure to the presented stimuli and evaluating their sense of presence. The first virtual environment represented a rollercoaster but this was no success, according to Drs. Schuemie. The second consisted of a swimming pool with a bridge but was considered not to be very realistic by the test persons. The third one integrated a glass elevator. In spite of the lack of realism, the swimming pool appeared to be the most effective environment. The test patients indicated the importance of having reference points nearby whereas they automatically tried to fill in the missing details.
In a second experiment, both a diving tower and a glass elevator were added to the virtual environment of the swimming pool. The team also took care to make the noise from virtual bathing people below sound less loud, in order to enhance the realism. A significant reduction of acrophobia was observed in the ten tested patients. Surprisingly, no correlation whatsoever between fear and effectiveness nor between sense of presence and effectiveness could be measured. These facts need more investigation, as Drs. Schuemie pointed out.
Next steps in the pilot study will include a controlled experiment to measure the relative effectiveness of Virtual Reality treatment and to determine the relationship between sense of presence and fear. The team of Drs. Schuemie equally plans to perform a full task analysis of the Virtual Reality therapy process. More details on this research at the Technical University of Delft are available in the VMW April 2000 article Virtual Reality Exposure Therapy to tackle "Vertigo" complex.