## 3 Results  
### Comparison Between MoCap and Ophthalmologic Tools  
Table 1 provides an overview of the mean values and standard deviations for head rotation and inclination angles in a static position, measured using ophthalmologic tools (i.e., digital goniometer for head rotation and eyeTilt application for head inclination) and the MoCap system in individuals with AHP. The table also includes PCC, ICC, RMSE, and accuracy values for the comparisons between the measurements from the ophthalmological tools and the MoCap system.  
Overall, the results highlight a high degree of concordance between ophthalmological tools and MoCap, supporting their validity for clinical assessment. The measurements demonstrate consistency across the systems, as reflected by the accuracy and RMSE values and by the absence of statistically significant inter-system differences (\(p>0.05\)) during the paired \(t\)-test. This consistency is further supported by PCC values, which indicate very strong, statistically significant correlations (PCC \(>0.8\); \(p<0.05\)) between MoCap and the other tools.  
Moreover, the ICC values for head rotation and head inclination further support the reliability of the ophthalmological tools compared to the MoCap system. Both ICC values fall within the \"good reliability\" range (\(0.75\leq\) ICC \(<0.90\)), indicating a strong level of consistency and agreement between the systems for these measurements.  
Figure 4 presents the Bland-Altman plots comparing the head rotation and inclination angles obtained from the digital goniometer and the eyeTilt application, respectively, and the MoCap system. The horizontal lines in the plots represent the mean difference and the LoA, defined as the mean difference \(\pm\) 1.96 * standard deviation. Conversely, the differences between the two paired values are plotted on the vertical axis, while their mean values are reported on the horizontal axis. Although a few measurements fall outside the LoA, no significant bias was observed, with 95% of the differences falling within the LoA. This indicates a generally good agreement between the compared systems, consistent with the results presented in Table 1.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{**Ophthalmological Tool**}} & \multirow{2}{*}{**MoCap**} & \multicolumn{2}{c}{\(p\)**-Value (\(t\)-Test)**} & \multirow{2}{*}{**PCC**} & \multirow{2}{*}{**Accuracy (\%)**} & \multirow{2}{*}{**ICC**} & \multirow{2}{*}{**RMSE (\({}^{\circ}\))**} \\  & & & & & & \\ \hline Head Rotation (\({}^{\circ}\)) & 0.60 \(\pm\) 10.20 & 1.53 \(\pm\) 6.48 & 0.538 & 0.86 \({}^{\ast}\) & 7.24 \(\pm\) 4.08 & 0.79 & 3.43 \\ Head Inclination (\({}^{\circ}\)) & 2.33 \(\pm\) 5.75 & 3.58 \(\pm\) 8.40 & 0.346 & 0.82 \({}^{\ast}\) & 7.83 \(\pm\) 3.78 & 0.77 & 5.00 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Mean and standard deviation values, \(p\)-values associated with the performed paired \(t\)-test, Pearson’s correlation coefficients (PCCs), accuracy, intraclass correlation coefficient (ICC), and root mean square error (RMSE) values for the head rotation and inclination angles measured with ophthalmological tools and the MoCap system. * = \(p<0.05\).  
Figure 4: Bland–Altman plots of the average value of head rotation (**a**) and head inclination (**b**) angles measured by MoCap and ophthalmological tools plotted against the differences between the systems.