Juhasz T, Kastis G A, Suárez C, Bor Z, Bron W E
Department of Physics, University of California, Irvine 92717, USA.
Lasers Surg Med. 1996;19(1):23-31. doi: 10.1002/(SICI)1096-9101(1996)19:1<23::AID-LSM4>3.0.CO;2-S.
Photodisruption in ocular media with high power pulsed lasers working at non-absorbing frequencies have become a well established surgical tool since the late seventies. Shock waves and cavitation bubbles generated by the optical breakdown may strongly influence the surgical effect of photodisruptive lasers. We have investigated the shock wave and cavitation bubble effects of femtosecond laser pulses generated during photodisruption in corneal tissue and water. The results are compared to those obtained with longer laser pulses.
STUDY DESIGN/MATERIALS AND METHODS: Laser pulses with 150 fs duration at approximately 620 nm wavelength have been focused into corneal tissue and water to create optical breakdown. Time-resolved flash photography has been used to investigate the dynamics of the generated shock waves and cavitation bubbles.
A rapid decay of the shock waves is observed in both materials with similar temporal characteristics and with a spatial range considerably smaller than that of shock waves induced by picosecond (or nanosecond) optical breakdown. Cavitation bubbles are observed to develop more rapidly and to reach smaller maximum diameter than those generated by longer pulses. In corneal tissue, single intrastromal cavitation bubbles generated by femtosecond pulses disappear within a few tens of seconds, notably faster than cavitation bubbles generated by picosecond pulses.
The reduced shock wave and cavitation bubble effects of the femtosecond laser result in more localized tissue damage. Therefore, a more confined surgical effect should be expected from a femtosecond laser than that from picosecond (or nanosecond) lasers. This indicates a potential benefit from the applications of femtosecond laser technology to intraocular microsurgery.
自20世纪70年代末以来，使用工作在非吸收频率的高功率脉冲激光对眼内介质进行光破碎已成为一种成熟的手术工具。光击穿产生的冲击波和空化气泡可能会强烈影响光破碎激光的手术效果。我们研究了角膜组织和水中光破碎过程中飞秒激光脉冲产生的冲击波和空化气泡效应。并将结果与使用更长激光脉冲获得的结果进行比较。
研究设计/材料与方法：波长约为620nm、持续时间为150fs的激光脉冲已聚焦到角膜组织和水中以产生光击穿。时间分辨闪光摄影已被用于研究产生的冲击波和空化气泡的动力学。
在两种材料中均观察到冲击波的快速衰减，其时间特性相似，空间范围明显小于皮秒（或纳秒）光击穿诱导的冲击波。观察到空化气泡比由更长脉冲产生的空化气泡发展得更快，并且达到的最大直径更小。在角膜组织中，飞秒脉冲产生的单个基质内空化气泡在几十秒内消失，明显快于皮秒脉冲产生的空化气泡。
飞秒激光的冲击波和空化气泡效应减弱，导致组织损伤更局限。因此，与皮秒（或纳秒）激光相比，飞秒激光应能产生更局限的手术效果。这表明飞秒激光技术应用于眼内显微手术具有潜在益处。
