Background Studies showed that 577 nm subliminal micropulse photocoagulation for retinal diseases is more effective and much safer than 577 nm laser,but its mechanism and sensitive target cells are still unelucidated.Objective This study was to compare the histomorphology changes of rabbit retinas following 577 nm subliminal micropulse excitation and 577 nm laser for retinal photocoagulation and offer a conference for the clinical application of 577 nm subliminal micropulse excitation.Methods Twenty-six Chinese pigment rabbits were randomly divided into normal control group (2 rabbits),577 nm laser photocoagulation group (6 rabbits) and subliminal micropulse photocoagulation group (18 rabbits),in which the rabbits from subliminal micropulse photocoagulation group were subgrouped into 9％,12％ and 15％ subthreshold photocoagulation groups according to the different workload rates,and retinal photocoagulation was performed based on grouping.No treatment was carried out in the normal control group.Fundus camera and OCT were obtained after photocoagulation,and the rabbits were sacrificed to prepare the specimen of eyeball wall.Hematoxylin and eosin staining was employed to examine the histopathological change of choroid and retina under the light microscope.Results The retinal morphology was normal on the fundus color photography and OCT in the normal control group.Obscure of retinal structure and slight edema of retinal neuroepithelial layer with obscure of retinal pigment epithelium (RPE) was found respectively in the 9％ and 12％ subthreshold photocoagulation group,and serious edema of retinal neuroepithelial layer with local RPE elevation was visible in the 15％ subthreshold photocoagulation group.The laser spot was invisible in various subliminal micro pulse groups.However,retinal photocoagulation spots,multifocal elevation of retinal layer and serious detachment of retinal neuroepithelium were found in the 577 nm laser group.Retinal histopathological examination revealed that the photoreceptors,bipolar cells and retinal ganglion cell (RGC) layers were normal,while choroidal vessel deformation and bleeding were visible in the 9％ and 12％ subthreshold photocoagulation groups,and only photoreceptor membrane swelling was seen in the 15％ subthreshold photocoagulation group.However,retinal structure abnormality was displayed in 577 nm laser group,including the structural disorders of inner and outer nuclear layers and RGC layer as well as thinning of RPE layer.Conclusions 577 nm nicropulse laser under threshold is sensitive for RPE and choroid rather than retina neurepithelium,which can play a treating role and also does not damage retina seriously.However,577 nm laser photocoagulation results in retinal structure damage.%背景 近年来研究表明,577 nm阈下微脉冲激光治疗视网膜疾病可达到传统577 nm激光光凝的治疗作用且对视网膜组织损伤小,但其具体作用机制和敏感的靶细胞尚未完全阐明. 目的 探讨和比较577 nm阈下微脉冲激光与577 nm激光光凝视网膜后成年中华黑兔视网膜组织形态学变化,为577 nm阈下微脉冲激光光凝在临床上的应用提供依据.方法 采用抽签法按照视网膜光凝条件不同将26只中华黑兔分为正常对照组(2只)、577 nm激光组(6只)和阈下微脉冲激光组(18只),其中阈下微脉冲激光组按照激光工作负载率的不同亚分为9％、12％和15％阈下微脉冲激光组,每组各6只,正常对照组不做任何处理.光凝后行彩色眼底照相及OCT检查,摘取兔眼球壁行苏木精-伊红染色,光学显微镜下观察兔脉络膜和视网膜组织结构的变化.结果 彩色眼底照相和OCT显示正常对照组兔眼视网膜组织结构清晰.9％阈下微脉冲激光组OCT扫描可见视网膜神经上皮层稍模糊;12％阈下微脉冲激光组光凝斑处视网膜神经上皮层轻度水肿,视网膜色素上皮(RPE)层稍模糊;15％阈下微脉冲激光组可见光凝斑处视网膜神经上皮层明显水肿,RPE层局限性隆起;各阈下微脉冲激光组彩色眼底照相均未见光凝斑.577 nm激光组兔眼彩色眼底照相可见灰白色光凝斑,OCT扫描层面可见视网膜呈多灶性隆起,视网膜各层组织结构模糊,伴浆液性神经上皮层脱离.视网膜组织病理学检查可见,与正常对照组兔眼相比,9％和12％阈下微脉冲激光组兔眼脉络膜血管变形或出血,但视细胞形态结构、双极细胞层和视网膜神经节细胞(RGC)层未见明显改变;15％阈下微脉冲激光组视细胞扁平状膜盘肿胀,双极细胞层和RGC层未见明显改变;577 nm激光组兔眼视细胞层、双极细胞层和RGC层结构紊乱,RPE层变薄.结论 577 nm阈下微脉冲激光对脉络膜层和RPE层具有高度选择性,视网膜光凝后对视网膜神经上皮层的损伤程度轻微,既可发挥治疗作用,又不损伤视网膜神经上皮;577 nm激光视网膜光凝可对视网膜全层造成损伤.
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