Background High intensity focused ultrasound (HIFU) is a novel noninvasive technique and it has been used to clinical treatment of solid tumors.However,whether it is safe to cure eye related diseases has not been reported.Objective This study was to explore the influence of HIFU on retinas of living rabbits after the irradiation on cornea,and provide a theoretical basis for the safety of clinical therapy.Methods Forty-one rabbits were involved.The corneal stroma of the right eye was irradiated by HIFU that was fixed in circular shape.The left eye with no treatment served as control group.Six rabbits were sacrificed at day 1,7,14,30,60 and 90 days after irradiation,respectively.The eyeballs of 3 rabbits were collected for paraffin imbedding.Histological method was then used to evaluate the structure of retina.Immunohistochemistry was used to determine the expression of Nogo-A.TUNEL method was carried out to examine cell apoptosis of different layers of retina.The retina of the rest 3 rabbits were collected to determine the contents of superoxide dismutase (SOD) and malondialdehyde (MDA).The retinal morphology of 5 rabbits were scanned by OCT and retinal thickness was recorded before irradiation and 1,7,14,30,60 and 90 days after irradiation.The use and care of experimental animals complied with Regulations on the Administration of Experimental Animals from National Ministry of Science and Technology.Results The number of retinal cell layers remained intact in the cornea of living rabbits after HIFU irradiation.The structure of each layer was densely and orderly arranged with clear borders between layers.The histological morphology of retinal tissues were the same among control eyes and experimental eyes at different time points.There was no significant difference in Nogo-A expression among control eyes and experimental eyes at different time points (Fgroup =0.672,P=0.413;Ftime =1.622,P=0.157).No significant difference was obtained in SOD activity and MDA contents among control eyes and experimental eyes at different time points (SOD:Fgroup =0.167,P =0.684;Ftime =0.074,P =0.996.MDA:Fgroup =0.005,P=0.946;Ftime =0.405,P =0.844).No TUNEL positive cell was obtained in each group.The thickness of retinal tissues showed no significant difference among before irradiation and 1,7,14,30,60 and 90 days after irradiation (F =0.150,P =0.988).Conclusions The irradiation of HIFU on the cornea of living rabbits shows no significant influence on the morphology and bioactive factors of retina.Therefore,the therapeutic application of HIFU irradiation on cornea is safe for retina.%背景 目前,高强度聚焦超声(HIFU)作为一种新兴的无创技术可通过辐照角膜以改变角膜曲率,从而矫治老视,然而其辐照角膜后对视网膜的安全性研究鲜见报道. 目的 探讨HIFU辐照活体兔眼角膜后对视网膜组织的影响,为其临床治疗的安全性提供实验依据. 方法 选择健康成年新西兰大白兔41只,用HIFU以圆环状定位辐照活体兔右眼角膜基质6 s,辐照环直径约为9 mm,左眼不接受干预,作为对照组.分别于辐照后第1、7、14、30、60、90天各处死6只实验兔,收集双侧眼球.取其中3只实验兔眼球剥取视网膜,行超氧化物歧化酶(SOD)活性和丙二醛(MDA)浓度检测;其余3只实验兔眼球常规石蜡包埋并行组织病理学、勿动蛋白A (Nogo-A)免疫组织化学及TUNEL凋亡染色观察.取5只实验兔分别于辐照前及辐照后第1、7、14、30、60、90天接受OCT扫描,观察视网膜厚度变化. 结果 实验兔对照眼可见视网膜分为10层,各层视网膜结构完整,边界清晰,细胞排列规则,HIFU辐照角膜后不同时间点实验眼视网膜组织学形态与对照眼比较无明显改变.对照眼和手术后各时间点实验眼视网膜神经节细胞层、内核层和外核层均有少量的Nogo-A蛋白表达,各组在术后不同时间点视网膜中Nogo-A表达量总体比较,差异均无统计学意义(F分组=0.672,P=0.413;F时间=1.622,P=0.157).各组兔眼在术后不同时间点视网膜匀浆中SOD活性及MDA浓度均无明显变化,总体比较差异均无统计学意义(SOD:F分组=0.167,P=0.684;F时间=0.074,P=0.996.MDA:F分组=0.005,P=O.946;F间间 =0.405,P=0.844).各组兔眼视网膜中未发现TUNEL阳性细胞.术前和术后1、7、14、30、60、90 d组兔眼视网膜厚度值分别为(148.20±1.79)、(148.10±1.79)、(147.60±1.52)、(148.00±1.58)、(147.80±1.64)、(147.40--.1.67)和(147.80±2.05) μm,总体比较差异无统计学意义(F=0.150,P=0.988).结论 HIFU辐照活体兔眼角膜后对视网膜组织形态、结构及各生物活性因子无明显影响,故HIFU辐照角膜改变角膜曲率以矫治老视对视网膜是安全的.
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