# Medical Augmented-Reality Visualizer for Surgical Training and Education in Medicine
## 4 Discussion  
The proposed system fulfills our design requirements and provides 3D perception of internal structures when either the operator's head or the phantom moves. The simulator provides content validity by clearly determining whether the training participant was able to trick the proper internal structure during the test. The duration of the packing procedure is measured, and faulty hits are recorded to differentiate between a good and bad performer (construct validity). Although no dedicated surveys were conducted, the user acceptability during the tests was very high. The educational impact  
Figure 17: Median time of a correct trick for each participant (on the **left**); a box-and-whisker diagram presenting the distribution of the values (on the **right**). The band in the box presents the median value for all participants. The boxes present the first and third quartiles while the ends of the whiskers show the minimal and maximal values without outliers in the group. Data points for which the distance to the box exceeds 1.5 of the interquartile range are marked as outliers. Figure 18: The number of correct attempts for each participant (on the **left**); a box-and-whisker diagram presenting the distribution of correct attempts (out of ten in total) for each participant (on the **right**). The boxes present the first and third quartiles while the ends of the whiskers show the minimal and maximal values in the group. was positive as shown by the failure rate distribution and median procedure time histograms. The cost of a single pricing procedure is mainly connected with the wear of the phantom and is approximately USD 0.50 (the cost of the system hardware is not considered here). Although the design requirements have been met, certain aspects of the presented solution can be further improved. In the current setup, the user must pay attention not to occlude the phantom edge from the PhTM camera. Moreover, the silicone mold may be deformed if mishandled and provide a faulty CSD. Furthermore, head tracking with a single marker makes the system sensitive to yaw/pitch/roll rotations of the head, and considerable rotations can lead to inaccuracy and distortion in the projected image. For a focused image to be formed on the retina, the eyes accommodate at a proper distance and adjust the required vergence. The allowable tolerance of the focusing distance for the observer to perceive of a clear image is \(\pm\)0.3D (diopter) [35], and the acceptable vergence error is at the level of 15-30\({}^{\prime}\) (arc minutes) [36]. Larger values impede the generation of stereoscopic vision [37]. Although small discrepancies do not cause the complete disappearance of binocular fusion, they notably undermine depth perception [38]. Therefore, the long-term use of conventional 3D displays causes fatigue and discomfort to the viewer [39; 40; 41]. Those symptoms may be caused by the lack of synchronization between vergence and accommodation [20]. In contrast, monoscopic visualization supported by motion parallax avoids these problems. After a few days of tests, we noticed declining performance of the participants, and one of them complained about a blunt needle. Then, we verified that this was the reason for the observed performance decay. In fact, after replacing the needle, the effectiveness returned to the expected levels. Furthermore, some students had difficulties interpreting the CT data displayed on the external LCD during the control experiment, possibly because of their inexperience. In addition, frozen pose detection was problematic, as some of students found it difficult to coordinate the pedal usage. On the other hand, some participants pointed out the low resolution of the projected data as the main drawback of the MARVIS system. Nevertheless, most participants claimed that using MARVIS led to easier and faster task completion by the projection-supported 3D perception and understanding of the spatial relationships between internal structures.