## 4 Discussion
Although this is not a clinically acceptable scenario, we wanted to minimize the unambiguity of the measurements. The results confirmed that elevated IOP increase the stiffness of the cornea, which is harder to deform [33]. Generally, the corneal displacement (MAD) and eye retraction (MER) amplitudes depend also on the strength of the stimulus. However, we observed that the relation between MAD (or MER) and the IOP became weaker (Spearman correlation coefficients are lower) for softer air puffs (Type 2 and Type 3) in comparison with regular air puff (Type 1). This suggests that it might be more challenging to estimate the IOP from air-puff tonometry with softer stimulus. However, recent studies showed that the application of computational models help to maintain the accuracy of IOP estimation by taking into account different air pressure loading for patient-specific parameters of the cornea [22; 34]. CRT increased with the IOP, which confirms that the start of deformation of eyes with higher IOP requires higher values of the air-puff pressure. In addition, the relation between CRT and IOP was not linear, and the influence of the air-puff amplitude on observed CRT was less defined. The results showed no statistically significant impact of the IOP on the CCT measured either before applying the stimulus or during the maximum cornea deformation, which is in line with the observations obtained in the in vivo study [35]. The maximum cornea speeds in the loading (CV\({}_{\text{L}}\)) and recovery (CV\({}_{\text{R}}\)) phase, as well as the time interval between them (\(\Delta\text{t}_{\text{v}}\)), were highly correlated with the IOP. Since the effective deformation of the cornea becomes lower with increasing IOP, CV\({}_{\text{L}}\), CV\({}_{\text{R}}\), and \(\Delta\text{t}_{\text{v}}\) also decrease with IOP. Similar results were obtained earlier in human corneas in vivo [35]. However, the analysis was performed only for Type 1 stimulation (air puff parameters used in standard devices). The identification of velocity peaks and their times was not reproducible enough to provide reliable results when the air puffs with lower amplitudes were used. The reproducibility of velocity-related parameters could be improved by applying cornea and sclera segmentation technique(s), providing better performance at low signal-to-noise ratio conditions or by implementing signal phase analysis. The latter boosts sensitivity towards very low amplitudes; thus, it would require phase-unwrapping and a higher A-scan rate. The tissue deformation is composed of loading and recovery phases. Accordingly, the return of the cornea to baseline position enables us to treat the process as a single cycle. Thus, air-puff induced cornea reaction can be plotted against the instant stimulus amplitude. The observed hysteresis is significantly affected by any offset, such as eye retraction. Retraction-corrected displacements allow us to avoid systematic errors in measurements of HA, which corresponds to the visco-elastic properties of corneal tissue. The HA decreased with the IOP and significant correlation coefficients for all types of the air puff have been found. It means that elastic properties dominated the corneal reaction when the IOP increased. However, like in the case of CRT, no particular relation between the air-puff type and HA was found for each IOP level. Finally, the correlations between the slope S and the IOP are similar to those observed for MAD. The findings from this ex vivo study have important implications for clinical practice, particularly in the assessment of IOP and corneal biomechanics. Softening the air-puff stimulus may be more comfortable for patients; however, the results indicate that some parameters quantifying the dynamic corneal response become more vulnerable to a reduction in correlation with IOP when a gentler air-puff is applied. Consequently, the accuracy of IOP estimation based on corneal deformation data could be compromised, potentially affecting the diagnostic reliability for conditions such as glaucoma.