Background. Prism adaptation therapy has been known to be effective to promote the recovery from neglect. However, the conventional prism therapy has a few shortcomings. Prism lens has to be changed to adjust the degree of deviation by the prism and the hand trajectory has to be masked during therapy. To solve these problems in conventional prism therapy, we developed virtual prism adaptation therapy using immersive virtual reality and depth-sense camera.

Methods. The developed system was applied to ten subacute stroke patients with hemispatial neglect (60.3±10.1 yrs old, M:F=6:4). The experiment consisted of 4 phases, which were non-prism, 5-min-prism (10-degree deviation), 5-min-prism (20-degree deviation) and 5-min-non-prism (post-adaptation). The median values of pointing deviations for 30-second-block in each phase were plotted. The cortical activation pattern was analyzed in each condition using the functional near-infrared spectroscopy with the block design.

Results. The pointing error in the first block of pointing during the 20-degree deviation mode was significantly higher (7.9±3.2) than that in the non-prism mode (1.4±7.3) (p=0.046). The pointing error in the first block of pointing during the post-adaptation phase was changed to the negative direction (-6.5±4.4) compared to the non-prism mode (p=0.028). The most significantly activated area during the last three phases in contrast to the non-prism phase was the area around the right premotor cortex (Brodmann area 6).

Conclusion. The virtual prism adaptation therapy could be a feasible system to solve the problems of conventional prism adaptation therapy. Further clinical trial to investigate the efficacy of this system is required.

Development and validation of virtual prism adaptation therapy in subacute stroke patients with hemispatial neglect