## 4 Discussion  
From the results obtained from the pump-probe propagation simulations, we identified an angular incidence tolerance (\(\pm\)5\({}^{\circ}\)) to achieve a good alignment of the setup proposed for the STM technique in the AC of a pig eye model. This alignment compromises to fulfill the cavitation zone and the reflection surface at the iris with the probe beam. Using a paraxial propagation simulation of the pump beam (WinLens3D), we found that the fluence onto the retina is \(\approx\)8.4\(\times\)10\({}^{-3}\) J/cm\({}^{2}\), considering a pump energy \(E_{B}\)= 13 mJ, a circular surface with radius \(\gamma\) (see Figure 6), reflective losses (\(\approx\)2.68%), losses by linear absorption in the ex vivo cornea (\(\approx\)38% [34] with \(\mu_{a}\) = 5.37 cm\({}^{-1}\) at 532 nm), and energy partition (\(\approx\)25% transmitted energy after the focal zone [19; 28]). This resulting laser fluence is about three orders of magnitude below the theoretical-experimental damage threshold for human retina, as reported by [PERSON] et al. [35] and [PERSON] et al. [36] (\(\approx\)1.3 to 2.3 \(\times\) 10\({}^{0}\) J/cm\({}^{2}\)) under different laser irradiation conditions, such as pulse duration, wavelength, and beam size. It is important to note that this value of the incident fluence onto the retina is just a first approximation of the real value, since the total energy losses and an estimate of the solid angle onto the retina must be considered. The results in Figure 7 show a remarkable difference in the temporal dynamics between the growth and collapse of the cavitation bubbles generated in a large volume and those generated in the close proximity to a solid boundary, i.e., cornea, iris, and/or crystalline. The presence of walls close to the cavitation bubble leads to the appearance of vapor jets after the first collapse, producing instability and asymmetry in the bubble [37]. Fragmentation of the bubble produces the appearance of multiple micro-bubbles [15] and interference effects due to shock waves and the cavitation bubbles' interactions with the walls. These effects after the first collapse time show up in the STM trace as a chaotic modulation on the signal. From Figure 7c, we found the threshold fluence (\(\approx\)6 kJ/cm\({}^{2}\)) that allows precise detection and measurement of the first collapse time. This fluence corresponds to an applied pump energy of 11 mJ and NA = 0.4. Figure 8 shows that the STM technique implemented in the AC of an ex vivo pig eye model produces consistent measurements of the collapse time (using averaged STM signals) for applied pressure within the IOP range; it also shows that these measurements hold for two different pig eye sizes (M and S), and can stand the effects of the adjacent walls [15] and the decrease in the volume of the AC due to the AE [30]. According to [PERSON] et al. [27] and [PERSON] (1989), the dynamical behavior of a cavitation bubble strongly depends on the dimensionless distance \(\gamma=s/R_{max}\), with \(R_{max}\) being the maximum bubble radius, and \(s\) the distance between the location of bubble formation and a solid wall. They found three situations for three values of \(\gamma\): For the first case (\(\gamma\) = 0.75), they saw that the wall avoids the full growth of the bubble and a vapor jet is not observed; in the second case (\(\gamma\) = 1.56), a counter-jet appears in the direction opposite to the growth of the bubble; in the third case (\(\gamma\) = 2.30), a jet appears moving towards the wall from the bubble. In both cases, the normal growth of the bubble is not prevented. In our experiments, we estimate that we are in the second case, where the walls (cornea, iris, and/or crystalline) and the AE do not appear to strongly affect the normal growth of the bubble, since we do not observe disturbance on the trend of the first collapse time measured at increasing pressure within the IOP range. Furthermore, the vapor jet does not cause damage to the surrounding walls.