Brinkmann R, Dröge G, Schröer F, Scheu M, Birngruber R
Medical Laser Center Lübeck GmbH, Germany.
Ophthalmic Surg Lasers. 1997 Oct;28(10):853-65.
Sclerostomy ab externo with pulsed laser systems is currently in phase II clinical trials. The authors investigated the ablation dynamics of tissue treated with pulsed laser systems in the mid-infrared range to estimate the extent of thermo-mechanical damage to the sclera and the anterior chamber.
Freshly harvested porcine eyes were used. A bare 400-micron fiber in direct contact with tissue was used for fistulization. Polarization light microscopy, fast-flash photography, as well as optical and acoustic transients were performed for analysis.
Substantial mechanical tissue deformation and dissections were found during pulsed laser ablation. The mechanical damage range within tissue far exceeds the pure thermal damage zone. Aspheric cavitation bubbles of up to 3 mm in length penetrate the anterior chamber after perforation. The cavitation demonstrates a significantly larger time constant in tissue than in water.
Early fistula occlusions due to iris adherences may be attributed to iris trauma caused by cavitation. In response to the findings of this study, the authors propose an automatic feedback system to control the ablation process and minimize secondary ocular tissue effects. With respect to the overall damage zones, a new continuous-wave, mid-infrared diode laser system seems to be superior to pulsed laser systems.
使用脉冲激光系统进行巩膜外造瘘目前正处于II期临床试验阶段。作者研究了用中红外波段脉冲激光系统治疗的组织的消融动力学，以评估对巩膜和前房的热机械损伤程度。
使用刚摘除的猪眼。一根与组织直接接触的400微米裸光纤用于造瘘。采用偏振光显微镜、快速闪光摄影以及光学和声学瞬态分析。
在脉冲激光消融过程中发现了明显的组织机械变形和切割。组织内的机械损伤范围远远超过纯热损伤区。穿孔后，长达3毫米的非球面空化气泡穿透前房。空化在组织中的时间常数明显大于在水中的时间常数。
虹膜粘连导致的早期瘘管阻塞可能归因于空化引起的虹膜损伤。针对本研究的结果，作者提出了一种自动反馈系统来控制消融过程并将眼部组织的继发效应降至最低。就整体损伤区域而言，一种新型连续波中红外二极管激光系统似乎优于脉冲激光系统。
