# Behavior of Generated Gas during Femtosecond Laser Lens Irradiation in Porcine Cadaver Eyes
## 3 Results
### Endoscopic Imaging  
When using the endoscope to observe behind the crystalline lens during laser irradiation (Figure 1), images showed that the gas generated by the laser irradiation coalesced and expanded rearward beyond the irradiation site, leading to the expansion of the posterior capsule (Figures 3a-d and 4a,b). The greater the amount of laser irradiation energy, the greater the amount of gas that was produced.  
Figure 3: Generated gas by laser irradiation coalesced and moved rearward and beyond the irradiation site, thereby causing the posterior capsule to expand. Excised lens that was irradiated by the laser was expanded as compared to the control lens. (**a–d**) Endoscopic image after laser irradiation in lens H. (**a**) Before laser irradiation. (**b**) At 2 s after laser irradiation. (**c**) After 10 s of laser irradiation. (**d**) At 44 s after laser irradiation. Yellow dotted line indicates the starting position of laser irradiation; white dotted line indicates the posterior capsule position before laser irradiation; white arrowheads indicate posterior capsule position after expansion. (**e,f**) Microscopic image of extracted lens. (**e**) Control lens Y. (**f**) Lens H after laser irradiation. Scale bar is 1 mm. Laser irradiation energy amount listed in parentheses.  
Figure 2: Although laser irradiation caused anterior chamber depth to become significantly shallower, there was no correlation with the amount of laser irradiation energy. (**a**) Box-plot diagram showing mean values of anterior chamber depth in the eye before and after laser irradiation. Boxes, interquartile range (difference between upper 75% and lower 25% quartiles); thick black lines, median; whiskers, highest and lowest values that were not outliers or extreme values. A significant difference was observed in ACD before and after laser irradiation (\(p\) = 0.042 \(<\) 0.05)). (**b**) There was no correlation between laser irradiation energy dose and ACD change ratio (\(p\) = 0.054 \(>\) 0.05).  
When the pressure exceeded the maximal pressure level of the capsule, the capsule fractured (Figure 4c-f, Video S1). The excised lens, which was irradiated with the laser, was expanded as compared to the control lens (Figure 3e,f). The crystalline lens achieved buoyancy due to the generated gas; if the buoyancy overcame the weight of the lens, the lens was able to float in the saline (Figure 5).  
Figure 4: The greater the laser irradiation energy was, the more gas was produced. If pressure exceeded maximal pressure levels of the capsule, it ruptured. (**a–c**) Endoscopic images of lens P during laser irradiation procedure. (**a**) Before laser irradiation. (b) Immediately before rupture by CBS during laser irradiation. (**c**) Immediately after rupture by CBS during laser irradiation. (**d**) Endoscopic images of lens P from the posterior pole of the eye after laser irradiation. White dotted line indicates capsule position before laser irradiation; white arrowheads indicate posterior position after expansion; yellow arrowheads indicate gas distribution after bursting into the vitreous cavity behind the ciliary body. (**e,f**) Microscopic image of extracted lens P. Error bar is 1 mm. Laser irradiation energy amount listed in parentheses.  
Figure 5: Generated gas caused the crystalline lens to become buoyant and overcome the weight of the lens, thereby allowing for it to float in the saline. Laser irradiation energy amount listed in parentheses.