## 4 Discussion  
In this paper, we present a way of assessing the quality of vision provided by PPLs with different power distributions using an eye-tracking-based system during the VA measurement. It is important to note that VA is subjective and depends on the participant's answer, whereas eye-tracking data is objective and provides quantitative data about eye movements, adding more information about the quality of vision with PPLs compared to the traditional VA evaluation method. The method proposed is based on the analysis of test duration, fixation time, and the number of fixations required to recognize the different optotypes of standard eye charts. The study showed that when evaluating the far-distance VA of participants using a PPL design with a wider far-distance visual area, the test duration, fixation time, and the number of fixations are reduced. Similarly, a PPL design with a wider near area provided a lower test duration, a lower fixation time, and a lower number of fixations during the evaluation of near-distance VA. It should be noted that the values of standard VA obtained with different PPL designs were not different with statistical significance. Although VA is considered a gold standard for the evaluation of optical quality, it seems insufficient alone to evaluate the quality of vision [17]. It is well known that sometimes clinicians report patients with high VA complaining about poor vision quality. Specifically, regarding the performance of PPLs, several studies have tried to evaluate differences in VA between different PPL designs without success. [PERSON] et al. [17] evaluated differences in VA at eight different off-axis positions on 20 presbyopic participants with two different PPL designs and did not find differences in VA between them. On the other hand, [PERSON] et al. [12] measured VA in the far and near regions in 95 presbyopic patients with a customized and a non-customized PPL design, and, once again, the results did not show differences in VA between both PPLs. Additionally, having a method that can determine differences in the visual performance provided by different PPL designs could help lens designers develop better lenses. Based on previous studies, we presume that the evaluation of eye movements during the performance of a specific task could be a sensitive indicator of the quality of vision provided by these lenses. In another study, [PERSON] et al. [27] evaluated differences between single-vision lenses and PPLs on 11 presbyopes. The subjects were required to read aloud a copy of printed text placed along their midline at 0.60 m. Eye movements were analyzed using the ISCAN computer-based system. The results showed an increase in fixation numbers \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**ANOVA Test for Eye Chart Size**} & \multicolumn{3}{c}{**Tukey HSD Comparisons for Eye Chart Size (\(p\)-Value)**} \\ \hline  & **Df** & **Mean Square** & **F-Ratio** & \(p\)**-Value** & **AVmax/Avmax-1** & **AVmax/Avmax-2** & **AVmax-1/Avmax-2** \\ \hline Test duration & 2 & 722.45 & 43.58 & \textless{}0.001 * & \textless{}0.001 * & \textless{}0.001 * & \textless{}0.001 * & \textless{}0.001 * \\ Fixation time & 2 & 644.19 & 47.40 & \textless{}0.001 * & \textless{}0.001 * & \textless{}0.001 * & \textless{}0.001 * \\ Fixation count & 2 & 312.56 & 10.96 & \textless{}0.001 * & 0.040 * & \textless{}0.001 * & 0.176 \\ \hline \hline \multicolumn{8}{c}{**ANOVA Test for Gaze Direction**} & \multicolumn{3}{c}{**Tukey HSD comparisons for gaze direction (\(p\)-value)**} \\ \hline  & **Df** & **Mean square** & **F-ratio** & \(p\)**-value** & **Centered/dominant** & **Centered/Non** & **Dominant/Non** \\  & 2 & 78.87 & 9.19 & \textless{}0.001 * & 0.003 * & 0.024 * & 0.778 \\ Fixation time & 2 & 58.05 & 7.94 & \textless{}0.001 * & 0.009 * & 0.021 * & 0.949 \\ Fixation count & 2 & 171.51 & 6.41 & \textless{}0.001 * & 0.007 * & 0.073 & 0.687 \\ \hline \hline \end{tabular}
\end{table}