Clinical Application to Improve the "Depth Perception Problem" by Combining Augmented Reality and a 3D Printing Model.

In our experience with intraoperative evaluation and educational application of augmented reality technology, an illusion of depth has been a major problem. To improve this depth perception problem, we conducted two experiments combining various three-dimensional models and holograms and the observation angles using an augmented reality device. Methods: In experiment 1, when observing holograms projected on the surface layer of the model (bone model) or holograms projected on a layer deeper than the model (body surface model), the observer's first impression regarding which model made it easier to understand positional relationships was investigated. In experiment 2, to achieve a more quantitative evaluation, the observer was asked to measure the distance between two specific points on the surface and deep layers from two angles in each of the above combinations. Statistical analysis was performed on the measurement error for this distance. Results: In experiment 1, the three-dimensional positional relationships were easier to understand in the bone than in the body surface model. In experiment 2, there was not much difference in the measurement error under either condition, which was not large enough to cause a misunderstanding of the depth relationship between the surface and deep layers. Conclusions: Any combination can be used for preoperative examinations and anatomical study purposes. In particular, projecting holograms on a deep model or observing positional relationships from not only the operator's viewpoint, but also multiple other angles is more desirable because it reduces confusion caused by the depth perception problem and improves understanding of anatomy.