Roach William P, Cain Clarence P, Narayan Drew G, Noojin Gary D, Boppart Stephen A, Birngruber Reginald, Fujimoto James G, Toth Cynthia A
Air Force Research Laboratory, Human Effectiveness Directorate, Optical Radiation Branch, Building 803, 8262 Hawks Road, Brooks Air Force Base, Texas 78253-5214, USA.
J Biomed Opt. 2004 Nov-Dec;9(6):1288-96. doi: 10.1117/1.1805554.
We investigate the relationship between the laser beam at the retina (spot size) and the extent of retinal injury from single ultrashort laser pulses. From previous studies it is believed that the retinal effect of single 3-ps laser pulses should vary in extent and location, depending on the occurrence of laser-induced breakdown (LIB) at the site of laser delivery. Single 3-ps pulses of 580-nm laser energy are delivered over a range of spot sizes to the retina of Macaca mulatta. The retinal response is captured sequentially with optical coherence tomography (OCT). The in vivo OCT images and the extent of pathology on final microscopic sections of the laser site are compared. With delivery of a laser pulse with peak irradiance greater than that required for LIB, OCT and light micrographs demonstrate inner retinal injury with many intraretinal and/or vitreous hemorrhages. In contrast, broad outer retinal injury with minimal to no choriocapillaris effect is seen after delivery of laser pulses to a larger retinal area (60 to 300 microm diam) when peak irradiance is less than that required for LIB. The broader lesions extend into the inner retina when higher energy delivery produces intraretinal injury. Microscopic examination of stained fixed tissues provide better resolution of retinal morphology than OCT. OCT provides less resolution but could be guided over an in vivo, visible retinal lesion for repeated sampling over time during the evolution of the lesion formation. For 3-ps visible wavelength laser pulses, varying the spot size and laser energy directly affects the extent of retinal injury. This again is believed to be partly due to the onset of LIB, as seen in previous studies. Spot-size dependence should be considered when comparing studies of retinal effects or when pursuing a specific retinal effect from ultrashort laser pulses.
我们研究了视网膜处激光束（光斑大小）与单个超短激光脉冲所致视网膜损伤程度之间的关系。根据以往研究，人们认为单个3皮秒激光脉冲对视网膜的影响在程度和位置上会有所不同，这取决于激光传输部位是否发生激光诱导击穿（LIB）。将580纳米激光能量的单个3皮秒脉冲以一系列光斑大小传输至猕猴的视网膜。通过光学相干断层扫描（OCT）依次捕捉视网膜反应。比较体内OCT图像与激光部位最终显微镜切片上的病理程度。当传输峰值辐照度大于LIB所需辐照度的激光脉冲时，OCT和光学显微镜图像显示视网膜内层损伤，并伴有许多视网膜内和/或玻璃体出血。相比之下，当峰值辐照度小于LIB所需辐照度时，将激光脉冲传输至较大视网膜区域（直径60至300微米）后，可观察到广泛的视网膜外层损伤，对脉络膜毛细血管的影响极小或无影响。当更高的能量传输导致视网膜内损伤时，更广泛的病变会延伸至视网膜内层。对染色固定组织的显微镜检查比OCT能提供更好的视网膜形态分辨率。OCT的分辨率较低，但可以在活体可见的视网膜病变上进行引导，以便在病变形成过程中随时间重复取样。对于3皮秒可见波长激光脉冲，改变光斑大小和激光能量会直接影响视网膜损伤程度。如先前研究所示，这再次被认为部分归因于LIB的发生。在比较视网膜效应的研究或追求超短激光脉冲产生特定视网膜效应时，应考虑光斑大小的依赖性。
