## 4 Discussion  
The aim of this study was to analyse whether excessive screen usage and COVID-19 infection correlate or influence the occurrence of acquired colour vision deficiencies in individuals with normal trichromatic vision. The Farnsworth-Munsell 100 Hue Test was employed to assess the colour vision capacity of the individuals. Furthermore, to ensure that the analysed population consisted solely of subjects without congenital colour vision deficiencies, the entire group was pre-evaluated with the Ishihara 32 Plates Test, which detects congenital colour vision defects. No subjects were excluded from the study as no congenital disabilities were detected in the group. The screening conducted using the Ishihara Test ensures that the data obtained and analysed solely represent potential acquired colour vision defects. Moreover, the screening patterns exhibited by the analysed subjects (average daily screen usage time) are consistent with the patterns of digital device usage reported in previous literature and are, therefore, representative and comparable. \begin{table}
\begin{tabular}{c c c} \hline \hline
**All Subjects** & **Subjects with COVID-19** & **Subjects No COVID-19** \\ \hline
5.40 \(\pm\) 1.58 & 5.46 \(\pm\) 1.62 & 5.32 \(\pm\) 1.51 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Values of \(\sqrt{\text{TES}}\) (Mean \(\pm\) SD) obtained for the complete group of subjects, for those who had contracted COVID-19, and for those who had not been infected by COVID-19. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Study** & **Year of Publication** &
\begin{tabular}{c} **Number of** \\ **Subjects Included** \\ \end{tabular} & \(\sqrt{\text{TES}}\) (Mean \(\pm\) SD) \\ \hline
[50] & 1982 & 29 & 5.69 \(\pm\) 2.07 \\
[48] & 1991 & 25 & 6.0 \(\pm\) 2.4 \\
[43] & 2001 & 30 & 7.50 \(\pm\) 2.41 \\
[49] & 2002 & 35 & 6.73 \(\pm\) 1.58 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Results obtained for \(\sqrt{\text{TES}}\) in previous works are to be compared with those obtained in previous works. To ensure the robustness of the presented results and to assert robust conclusions, all data obtained in the study have been doubly validated. This dual approach to result comparison ensures the reliability of the study and its conclusions. Firstly, a comparison was made between the obtained data and external data from other studies. The data were compared with data obtained in previous studies for populations of subjects within the same age range and with a very similar population size (around 50 subjects). The mean value of \(\sqrt{\text{TES}}\) obtained was compared with the mean value of \(\sqrt{\text{TES}}\) from subjects within the same age range in four previously published works. It is crucial to note that the comparison was conducted with studies from years (before 2003) in which the subjects were not affected by COVID-19 and did not undergo regular screening. Therefore, the comparison data can be considered as an optimal reference group. Secondly, an exhaustive internal analysis of the collected dataset was performed. On the one hand, the mean value of \(\sqrt{\text{TES}}\) was calculated for the analysed subjects, distinguishing between those who had experienced COVID-19 and those who had not. Both values showed no significant differences. On the other hand, a comprehensive statistical analysis of the dataset was conducted, examining both quantitative and qualitative aspects. This analysis of the relationships between the variables studied reveals that neither gender, COVID-19 infection, nor digital screen usage time are related to the occurrence of acquired colour vision defects. From the statistical analysis, we also addressed the effect of conducting the Ishihara Test on physical and digital supports, thus validating the use of digital support for administering the Ishihara Test. It is worth noting and emphasising the novelty of the study conducted as it is the first to comprehensively analyse whether excessive screen usage can be related to the increase in acquired colour vision deficiencies.