COLA 2015 International Conference on Laser Ablation 2015 31 August – 4 September 2015 Cairns, Australia
PROGRAM HANDBOOK
National Library of Australia Cataloguing-in-Publication entry
2
Creator:
Conference on Laser Ablation (13th : 2015 : Cairns, Qld.)
Title:
Conference on laser ablation 2015 : program handbook / Prof Andrei Rode.
ISBN:
978 0 64694 286 5 (paperback)
Subjects:
1. Laser ablation—Congresses. 2. Lasers—Industrial applications—Congresses.
Other creators/ contributors:
Rode, Andrei.
Dewey number:
621.366
13th Conference on Laser Ablation—COLA-2015 | PROGRAM HANDBOOK
P-143
Photodisruption of the elastic membrane with the laser-induced cavitation bubble dynamics: an optodynamic study G. Hawlina1, B. Drnovšek-Olup1, J. Možina2, P. Gregorčič*2 Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1525 Ljubljana, Slovenia Faculty of Mechanical Engineering, University of Ljubljana, Aškerčeva 6, 1000 Ljubljana, Slovenia E-mail:
[email protected] 1
2
Nd:YAG laser photodisruption with nanosecond laser pulses and energies of few millijoules is a wellestablished tool for intraocular surgery, such as treatment of posterior capsule opacification (PCO) or latepostoperative capsular bag distension syndrome (CBDS) [1]. The PCO and CBDS are post-operative complications of cataract surgery that affects the visual function. The PCO develops due to the lens epithelial cells remaining in the capsular bag after the cataract surgery [2]. Clinically, there are two basic morphological types of PCO, the fibrosis type and the pearl type, which have different cellular origins [3]. On the other hand, the visual function is affected by CBDS due to the accumulation of liquefied material in a closed space between the posterior capsule and the intraocular lens optic [4]. The most effective treatment for PCO and CBDS is a Nd:YAG laser capsulotomy, where the excitation pulse is focused just behind the posterior capsule (typically 100-200 m). Here, a high-intensity laser pulse induces an optical breakdown resulting in a microexplosion initiated by plasma formation [5]. The plasma expansion is followed by different optodynamic phenomena, such as a shock wave and the cavitation bubble. When a cavitation bubble expands to its maximum volume, it starts to collapse due to the liquid pressure. Under suitable conditions [6, 7] the collapsing bubble develops a liquid jet responsible for the posterior capsule disruption. The procedure is repeated several times, e.g., in a cruciate pattern. In such a way, a central opening in the opacified posterior capsule clears the visual axis. On the other hand, the optodynamic phenomena are responsible also for unwanted collateral effects on many delicate structures which are located very close to the breakdown region. The bubbles dynamics is determined by (i) the distance between the bubble’s center and the boundary; and the (ii) boundary conditions. In the case of the laser capsulotomy, the boundary conditions depend on the PCO types - fibrosis, pearl or mixed type – which differ by the mechanical properties as well by the distance between the posterior capsule (a thin membrane) and the intraocular lens (a solid boundary). In our previous in-vivo study [1], we have shown that both, the PCO type and the distance between the intraocular lens and the posterior capsule significantly affect the total-pulse energy needed to perform the capsulotomy. Understanding of the physical mechanisms that are responsible for these effects is important, since lower total-pulse energy means fewer side effects. However, in our previous in-vivo study [1] we have found that an ex-vitro experiment under more reproducible and controllable conditions should be performed to clarify the main mechanisms that are responsible for the posterior capsule opening. In this contribution we will use a high-speed shadowgraphy and a laser-beam-transmission probe [8] to study the laser-induced cavitation bubble dynamics near a solid boundary with a thin elastic membrane. As an excitation source we use a Nd:YAG laser with pulse duration of 6 ns and energy up to 12 mJ, designed for intraocular photodisruption. Our study includes the investigation of membrane and solid boundary photodisruption at different distances between the boundary and the membrane. In such a way we designed an ex-vitro model of an intraocular laser surgery, where the distance between the posterior capsule (a thin membrane) and an intraocular lens (a solid boundary) varies form few micrometers (as in the case of the fibrosis PCO type) to several hundreds of micrometers as in the case of CBDS [1]. On the other hand, the perforation of the membrane simulates the wanted effect of the posterior capsule opening, while the damages of the solid boundary represent the side effects that should be avoided during the laser capsulotomy. 1 2 3 4 5 6 7 8
G. Hawlina, D. Perovšek, B. Drnovšek-Olup, J. Možina and P. Gregorčič, “Intraocular Photodisruption with Picosecond and Nanosecond Laser-Pulses - Tissue Effects in Cornea, Lens, and Retina” BMC Ophthalmology 14, 131 (2014). E. J. Hollick, D. J. Spalton, P. G. Ursell, and M. V. Pande, “Lens epithelial cell regression on the posterior capsule with different intraocular lens materials” Brit. J. of Ophthalmol. 82, 1182 (1998). D. J. Apple, K. D. Solomon, M. R. Tetz, E. I. Assia, E. Y. Holland, U. F. C. Legler, J. C. Tsai, V. E. Castaneda, J. P. Hoggatt, J. P., and A. M. P. Kostick, “Posterior Capsule Opacification” Surv Ophthalmol 37, 73 (1992). K. Miyake, I. Ota, S. Ichihashi, S. Miyake, Y. Tanaka, and H. Terasaki, “New classification of capsular block syndrome” J. Cataract. Refr. Surg. 24, 1230 (1998). A. Vogel, M. R. C. Capon, M. N. Asiyovogel, and R. Birngruber, “Intraocular Photodisruption with Picosecond and Nanosecond Laser-Pulses - Tissue Effects in Cornea, Lens, and Retina” Invest. Ophth. Vis. Sci. 35, 3032 (1994). Y. Tomita, A. Shima, “Mechanisms of impulsive pressure generation and damage pit formation by bubble collapse” J. Fluid. Mech. 169, 535 (1986). A. Vogel, W. Lauterborn, R. Timm, “Optical and acoustic investigations of the dynamics of laser-produced cavitation bubbles near a solid boundary” J. Fluid. Mech. 206, 299 (1989). P. Gregorčič, M. Jamšek, M. Lukač, M. Jezeršek, “Synchronized delivery of Er:YAG-laser-pulse energy during oscillations of vapor bubbles, J. LA&HA 2014, 14 (2014).
