Ren Q, Simon G, Parel J M
Department of Ophthalmology, University of California, Irvine 92715.
J Refract Corneal Surg. 1994 Sep-Oct;10(5):529-39.
Laser photothermal keratoplasty has been studied as a potential refractive procedure. The purpose of this study is to investigate the histological response to various laser treatments including geometrical patterns, radiant exposure levels, and pulse numbers.
A noncontact laser photothermal keratoplasty system was used in this study. Epithelial and endothelial response to the laser photothermal keratoplasty annulus treatment pattern were studied on an owl monkey model with a 5-millimeter annulus ring pattern, 8 J/cm2, 25 consecutive pulses at 1 Hz. Epithelial and endothelial response to the laser photothermal keratoplasty spot pattern were then studied and compared on cat and rabbit models for safety monitoring. One pulse and five consecutive pulses of eight different radiant exposures (5.00 J/cm2 to 18.01 J/cm2) were applied on each cornea. A cadaver eye model was used to study the collagen shrinkage induced by the laser spot treatment following the same protocol as the cat and rabbit model. Finally, the biological healing response to the laser photothermal keratoplasty treatment with the optimal laser parameters obtained in our experiment was studied on the cat model. Five cats were treated by the laser photothermal keratoplasty procedure with eight spots on a 3-millimeter ring, 15.6 J/cm2, and 1 pulse.
Epithelial and endothelial damage were observed after annulus treatment on an owl monkey's cornea at 8 J/cm2, 25 pulses, and after spot treatment on cat and rabbit corneas at 18.01 J/cm2, five pulses. No endothelial damage was observed on cat corneas for the single pulse treatment at 18.01 J/cm2. For the tissue shrinkage study, no laser photothermal keratoplasty lesion could be detected for a radiant exposure setting below 10.26 J/cm2. Histological cross-sections showed that the five-pulse treatment reached the endothelial layer at a radiant exposure of 13.4 J/cm2, while no single pulse treatment reached the endothelium for the radiant exposure range (5 J/cm2 to 18 J/cm2) studied. The cat model showed that the laser-induced mechanical octagonal stress-lines by collagen shrinkage were maintained after 3 months. The histological sections across the lesion showed a denser keratocyte population indicating scar formation.
The volume of collagen shrinkage, its location, and its geometrical shape can be accurately and precisely controlled by a 2.10-micrometer Ho:YAG laser coupled to an optical delivery system.
激光光热角膜成形术已作为一种潜在的屈光手术进行了研究。本研究的目的是调查对包括几何图案、辐射暴露水平和脉冲数在内的各种激光治疗的组织学反应。
本研究使用了一种非接触式激光光热角膜成形术系统。在一只猫头鹰猴模型上，采用5毫米环形图案、8 J/cm²、1赫兹连续25个脉冲的参数，研究了激光光热角膜成形术环形治疗模式对上皮和内皮的反应。然后，在猫和兔模型上研究并比较了激光光热角膜成形术点状模式对上皮和内皮的反应，以进行安全性监测。在每只角膜上施加8种不同辐射暴露量（5.00 J/cm²至18.01 J/cm²）的1个脉冲和5个连续脉冲。使用尸体眼模型，按照与猫和兔模型相同的方案，研究激光点状治疗引起的胶原收缩。最后，在猫模型上研究了对我们实验中获得的最佳激光参数的激光光热角膜成形术治疗的生物愈合反应。5只猫接受了激光光热角膜成形术治疗，采用3毫米环上的8个点、15.6 J/cm²和1个脉冲。
在猫头鹰猴角膜上以8 J/cm²、25个脉冲进行环形治疗后，以及在猫和兔角膜上以18.01 J/cm²、5个脉冲进行点状治疗后，观察到上皮和内皮损伤。在18.01 J/cm²进行单脉冲治疗时，猫角膜未观察到内皮损伤。对于组织收缩研究，在辐射暴露设置低于10.26 J/cm²时，未检测到激光光热角膜成形术损伤。组织学横截面显示，在辐射暴露量为13.4 J/cm²时，5脉冲治疗到达内皮层，而在所研究的辐射暴露范围（5 J/cm²至18 J/cm²）内，单脉冲治疗均未到达内皮。猫模型显示，激光诱导的胶原收缩产生的机械性八角形应力线在3个月后仍存在。病变处的组织学切片显示角膜细胞群体更密集，表明形成了瘢痕。
通过与光学传输系统耦合的2.10微米钬:钇铝石榴石激光，可以准确精确地控制胶原收缩的体积、位置及其几何形状。
