Brown D B, O'Brien W J, Schultz R O
Department of Ophthalmology, Medical College of Wisconsin, Milwaukee 53226.
Cornea. 1994 Nov;13(6):471-8.
This study examines corneal ablations produced by the neodymium doped yttrium-lithium-fluoride (Nd:YLF) picosecond laser. The laser delivers a 1-KHz, 40-ps pulsed, 1,053-nm wavelength beam (with energy measured in microjoules) to a 15-microns diameter spot size. The ablation mechanism is by plasma formation, which generates acoustic shock waves. Using enucleated rabbit (n = 25) and human donor eyes (n = 29), corneas were examined after tissue ablation at energies ranging from 40 to 300 microJ per pulse with various programmed ablation depths and patterns. The histologic data were collected using light microscopy and transmission electron microscopy. The tissue effects and Nd:YLF laser functions studied were ablation thresholds, cutting ability, programmed ablation depth accuracy, and acute endothelial effects. Our study showed histologic ablation thresholds for the following human corneal layers: epithelium = 7.15 +/- 0.05 x 10(11) W/cm2 (34.1 +/- 8.1 J/cm2 per pulse, 50 microJ per pulse); Bowman's layer = 1.33 +/- 0.29 x 10(12) W/cm2 (58.5 +/- 3.3 J/cm2 per pulse, 100-110 microJ per pulse); stroma and endothelium = 7.10 x 10(11) W/cm2 (28.4 J/cm2 per pulse, 50 microJ per pulse). Depth of corneal ablation was found to be directly related to energy and independent of programmed ablation depth. This study shows the endothelial loss in rabbit corneas by energy beams (50 microJ per pulse) focused 100 microns from this layer.
本研究考察了掺钕钇锂氟化物（Nd:YLF）皮秒激光产生的角膜切削。该激光发射频率为1千赫兹、脉冲宽度为40皮秒、波长为1053纳米的光束（能量以微焦耳计量），光斑直径为15微米。其切削机制是通过形成等离子体，进而产生声冲击波。使用摘除的兔眼（n = 25）和人类供体眼（n = 29），在每脉冲能量范围为40至300微焦耳、具有各种设定切削深度和模式的组织切削后检查角膜。使用光学显微镜和透射电子显微镜收集组织学数据。所研究的组织效应和Nd:YLF激光功能包括切削阈值、切割能力、设定切削深度准确性和急性内皮效应。我们的研究显示了以下人类角膜层的组织学切削阈值：上皮 = 7.15 +/- 0.05 x 10(11) W/cm2（每脉冲34.1 +/- 8.1 J/cm2，每脉冲50微焦耳）；Bowman层 = 1.33 +/- 0.29 x 10(12) W/cm2（每脉冲58.5 +/- 3.3 J/cm2，每脉冲100 - 110微焦耳）；基质和内皮 = 7.10 x 10(11) W/cm2（每脉冲28.4 J/cm2，每脉冲50微焦耳）。发现角膜切削深度与能量直接相关，且与设定切削深度无关。本研究显示了兔眼角膜因距离该层100微米聚焦的能量束（每脉冲50微焦耳）导致的内皮损失。
