兔视网膜多波长激光光凝术后OCT图像与组织病理学图像的比较

Comparison of optical coherence tomography images and histopathology images after multi-wavelength laser in rabbits’ retina

目的探讨不同波长激光光凝术后视网膜、脉络膜结构的光学相干断层成像(optical coherence tomography,OCT)与组织病理学变化的相关性。方法有色兔36只,左眼为空白对照组,右眼为实验组,实验组随机分3组,分别用绿光、黄光、红光激光光凝视网膜后极部,激光反应斑Ⅲ级,光斑直径300μm,光斑间距300μm,曝光时间200ms。于光凝后1h、7d、14d、28d分别对光凝区行OCT和组织病理学检查。结果组织病理学检查:3种激光光凝后1h,视网膜、脉络膜组织不同程度受到破坏:绿光光凝斑处主要表现为脉络膜毛细血管轻度扩张,视网膜色素上皮(retinal pigment epithelium,RPE)层线性结构消失,光感受器细胞层结构紊乱,外核层见核固缩;黄光光凝斑处主要表现为脉络膜毛细血管扩张明显,RPE层色素大量缺失,光感受器细胞层内、外节结构紊乱,内、外核层见核固缩;红光光凝斑处主要表现为脉络膜血管大部分扩张,内、外核层细胞缺失。随后,3种激光激光斑处RPE细胞、Müller细胞及成纤维细胞增生修复光凝区。OCT图像:3种激光光凝后1h,脉络膜组织的反射均显示不清,视网膜失去了其正常组织结构的划分,视网膜神经上皮层(retinal neuroepithelial layer,RNL)全层增厚、高反射;绿光、黄光、红光光斑处RNL厚度分别为(265.81±5.39)μm、(227.90±6.11)μm、(193.76±8.76)μm,与光凝前的(149.43±6.80)μm相比,差异均有统计学意义(均为P<0.01);绿光光凝斑处见RPE层光带基本消失,黄光光凝斑处见RPE层光带连续性大部分中断,红光光凝斑处RPE层光带只见连续性部分中断。随后,3种激光斑处RNL全层向光凝斑中心牵拉凹陷,视网膜内RPE反射不断增多,遮挡脉络膜组织反射。结论激光光凝后光凝斑OCT图像变化与组织病理学结构的变化具有一致性,可作为激光光凝后活体观察视网膜及脉络膜组织结构变化的影像学工具之一。不同波长的激光作用于眼底的组织学深度不同。

Objective To study the correlation between optical coherence tomography（OCT） and histopathology of construction of retina and choroid after multiwavelength laser. Methods Thirty-six pigmented rabbits were involved in the experiment. Their left eyes were treated as the blank control group and their right eyes were treated as the experimental group. The rabbits in experimental group were divided into three groups and were respectively photocoagulated at posterior pole by green, yellow and red laser with laser lesion effect of grade 81 photocoagulated spots in right eyes, the laser beam diameter was 300μm, spot spacing was 300 μm and time of exposure was 200ms. Then photo-coagulation region was examined by OCT and histopathology at 1 hour,7 days,14 days and 28 days,respectively, Results Histopathological changes：at l hour after all laser photocoagulation,the retina and choroid tissue subjected to different degrees of damage. In green laser lesions, changes were mainly restricted to choroid capillaries with moderate dilatation, the linear structure of RPE layer disappeared, the inner and the outer segments of photoreceptors were disordered and the pyknotic nuclei was found in outer nuclear layer ;in yellow laser lesions, changes were mainly restricted to choroid capillaries with serious expansion, much pigment of RPE was lost, the inner and the outer segments of photoreceptors were severely disordered and the pyknotic nuclei was found in inner and outer nuclear layer; in red laser lesions, changes were mainly restricted to most choroid vessels with obvious dilatation, and many cells in the inner and out nuclear layers were lost. Subsequently the proliferation of RPE, Muller cells and fibroblasts repaired the destroyed areas of retina. OCT images：at 1 hour after three laser photocoagulation, the reflectivity of choroid tissue could not be identified.Retinal structure and delineation of the individual layers comprising the retina were lost. All lesions were characterized by high reflectivity throughout the full thickness of the neurosensory tissue. Compared with the preoperation,the average thickness of neurosensory layers of green, yellow and red laser lesions were （ 255.81 ± 5.39 ）μm, （ 227.90 ± 5. 11 ） μm and （ 193.75 ± 8.75 ）μm and there was significant difference between them all （ all P 〈 0.01 ）. In green laser lesions, the RPE layer almost vanished;in yellow laser lesions,the RPE layer was mostly continously interrupted,in red laser lesions,the RPE layer was partly continously interrupted. Subsequently, strong contraction through the full thickness of the neurosensory layers was observed. The RPE reflectivity in the retina increased continuely, which sheltered choroid tissue reflectivity. Conclusion After the photocoagulation,the images obtained from OCT and histopathology are consistent and can be used clini- cally as a imageology measure to follow the constrction changes of retina and choroid. Different wavelength lasers reach parts of fundus differently.