Roider J, Lindemann C, Laqua H, Birngruber R
Department of Ophthalmology, Medical University of Lübeck, Germany.
Graefes Arch Clin Exp Ophthalmol. 1998 Mar;236(3):213-9. doi: 10.1007/s004170050067.
The aim of this study was to investigate whether selective damage the RPE while sparing the adjacent photoreceptors is possible with repetitive 200-ns pulses of Nd:YAG laser (532 nm) and what potential side effects can be expected with higher pulse energies.
We irradiated the retinas of 19 eyes of 10 chinchilla rabbits with 500 pulses from a Nd:YAG laser, each 200 ns in duration, at a repetition rate of 500 Hz (158 microns, 0-120 microJ). Threshold curves for different effects were established. Representative lesions were investigated by light and transmission electron microscopy.
It was possible to produce lesions, which were only visible by fluorescein angiography. The ED50 threshold energy per pulse for visibility by fluorescein angiography was 2.1 microJ per pulse, for visibility by ophthalmoscopy 8.6 microJ. Bubble formation, an uncommon phenomenon in retinal photocoagulation, occurred at energies of 15-25 microJ. Hemorrhage occurred at surprisingly high energy levels of more than 100 microJ. Histology performed on lesions visible only by angiography showed damage primarily to the RPE and outer segments, with very little damage to some inner segments dependent on the energy used.
Selective RPE damage is possible with repetitive 200-ns laser pulses and appropriate energy; however, the collateral damage to the adjacent retina is more pronounced than with repetitive microsecond laser pulses. There is no risk of hemorrhage of retinal photocoagulation with the repetitive 200-ns laser pulses at low energy levels which would be used clinically.
本研究的目的是探讨使用重复的200纳秒钕：钇铝石榴石激光（532纳米）脉冲是否能够选择性损伤视网膜色素上皮（RPE）同时 sparing 相邻的光感受器，以及更高脉冲能量可能会带来哪些潜在副作用。
我们用钕：钇铝石榴石激光的500个脉冲照射了10只龙猫兔子的19只眼睛，每个脉冲持续时间为200纳秒，重复频率为500赫兹（158微米，0 - 120微焦）。建立了不同效应的阈值曲线。通过光镜和透射电子显微镜对代表性病变进行了研究。
能够产生仅通过荧光素血管造影可见的病变。荧光素血管造影可见性的每个脉冲的半数有效剂量（ED50）阈值能量为每个脉冲2.1微焦，检眼镜可见性为8.6微焦。气泡形成是视网膜光凝中不常见的现象，在15 - 25微焦的能量水平时出现。出血发生在超过100微焦的令人惊讶的高能量水平。对仅通过血管造影可见的病变进行的组织学检查显示，主要损伤为RPE和外段，根据所用能量的不同，一些内段有非常小的损伤。
使用重复的200纳秒激光脉冲和适当的能量可以实现选择性RPE损伤；然而，与重复的微秒激光脉冲相比，对相邻视网膜的附带损伤更为明显。在临床使用的低能量水平下，重复的200纳秒激光脉冲不会有视网膜光凝出血的风险。
