Ren Q, Simon G, Parel J M
Department of Biomedical Engineering, College of Engineering, University of Miami, Coral Gables, FL 33124-0621.
Ophthalmology. 1993 Dec;100(12):1828-34. doi: 10.1016/s0161-6420(93)31390-4.
Replacing the gas argon fluoride (193 nm) excimer laser with a solid-state laser source in the far-ultraviolet spectrum region would eliminate the hazards of a gas laser and would reduce its size, which is desirable for photorefractive keratectomy. The authors investigated corneal reshaping using a frequency-quintupled (213 nm) pulsed (10 ns) neodymium:YAG laser coupled to a computer-controlled optical scanning delivery system.
A 250 +/- 15-mJ/cm2 radiant exposure was used to ablate a 5-mm optical zone in human cadaver eyes and rabbit eyes. The 213-nm laser pulses were delivered through and shaped by a computer-controlled optical scanning delivery system, producing a 0.5-mm spot with a quasi-Guassian energy distribution on the cornea. Corneal surface changes were documented by computer-assisted corneal topography. Light microscopy, scanning electron microscopy, and transmission electron microscopy were performed to examine the effects on corneal surface quality and cellular components.
Corneal topographic measurements showed myopic corrections ranging from 2.3 to 6.1 diopters. Results of postoperative examination with the slit lamp and operating microscope demonstrated a smoothly ablated surface without corneal haze. Histologic results showed a smoothly sloping surface without recognizable steps. The surface quality and cellular effects were similar to that of previously described excimer photorefractive keratectomy.
The authors demonstrated that an ultraviolet (213-nm) solid-state laser coupled to an optical scanning delivery system is capable of reshaping the corneal surface with smooth transition. The scanning beam delivery system may offer the advantage of producing spatially resolved, customized, aspheric corrections to optimize the quality of vision after photorefractive keratectomy.
在远紫外光谱区域用固态激光源替代气体氟化氩（193纳米）准分子激光，将消除气体激光的危害并减小其尺寸，这对于屈光性角膜切除术是可取的。作者研究了使用倍频（213纳米）脉冲（10纳秒）钕：钇铝石榴石激光与计算机控制的光学扫描传输系统相结合进行角膜重塑。
使用250±15毫焦/平方厘米的辐射曝光量对人尸体眼和兔眼的5毫米光学区进行消融。213纳米的激光脉冲通过计算机控制的光学扫描传输系统传输并成形，在角膜上产生具有准高斯能量分布的0.5毫米光斑。通过计算机辅助角膜地形图记录角膜表面变化。进行光学显微镜、扫描电子显微镜和透射电子显微镜检查以评估对角膜表面质量和细胞成分的影响。
角膜地形图测量显示近视矫正范围为2.3至6.1屈光度。裂隙灯和手术显微镜术后检查结果显示表面消融平滑，无角膜混浊。组织学结果显示表面平滑倾斜，无明显台阶。表面质量和细胞效应与先前描述的准分子激光屈光性角膜切除术相似。
作者证明，与光学扫描传输系统相结合的紫外（213纳米）固态激光能够使角膜表面平滑过渡地重塑。扫描光束传输系统可能具有产生空间分辨、定制、非球面矫正的优势，以优化屈光性角膜切除术后的视觉质量。
