Lorenz B, Birngruber R, Vogel A
Fortschr Ophthalmol. 1989;86(6):644-54.
The penetration depth of laser light into the fundus is dependent on the wavelength. Thereby, the profile of damage depends on the absorption and on the temperature profile. It has been demonstrated earlier that wavelength-dependent differences in penetration depth are hard to detect ophthalmoscopically or histologically in severe lesions in Chinchilla gray rabbits. Therefore in this study, the wavelength-dependent exposure powers necessary for (1) similar retinal effects and (2) similar choroidal effects were compared. The resulting wavelength-dependent differences were smaller than expected-due to at least three reasons: (1) predominance of the temperature profile over the absorption profile for clinically useful exposure times; (2) light scatter in the retina in relationship to the exposure time (and wavelength?): (3) changes in the choroidal geometry in relationship to the exposure time and wavelength. Nevertheless, it appears to be possible to spare the retina somewhat by using longer wavelengths. In order to evaluate the clinical situation experimentally despite the fact that the human choroid is about three times thicker than the rabbit choroid, a geometrical model has been developed. The results indicate that the retina is less damaged using Nd:YAG lasers than using argon lasers when similar choroidal effects are produced.
激光进入眼底的穿透深度取决于波长。因此，损伤情况取决于吸收情况和温度分布。此前已证明，在灰鼠兔的严重病变中，很难通过检眼镜检查或组织学方法检测到穿透深度的波长依赖性差异。因此，在本研究中，比较了产生（1）相似视网膜效应和（2）相似脉络膜效应所需的波长依赖性曝光功率。由于至少三个原因，由此产生的波长依赖性差异小于预期：（1）在临床有用的曝光时间内，温度分布比吸收分布占主导地位；（2）视网膜中的光散射与曝光时间（以及波长？）有关；（3）脉络膜几何形状与曝光时间和波长有关。然而，使用较长波长似乎有可能在一定程度上保护视网膜。尽管人类脉络膜比兔脉络膜厚约三倍，但为了通过实验评估临床情况，已开发了一个几何模型。结果表明，当产生相似的脉络膜效应时，使用Nd:YAG激光对视网膜的损伤比使用氩激光小。
