后极部巩膜内铁异物对视网膜及视神经影响的实验研究

Influence of posterior intrascleral iron foreign body on rabbit retina and opticus

背景铁质异物嵌在眼球壁在临床上时有发生，目前认为应尽快手术以免造成眼铁质沉着症。动物实验证实小的球壁铁质异物短期内对视网膜和视神经并不产生严重影响，因此是否必须手术取出仍是值得探讨的问题。目的评估兔眼后极部巩膜内植入铁异物对视网膜及视神经的影响。方法选取健康成年日本大耳白兔12只，采用随机数字表法分为无锈铁片组和有锈铁片组。以右眼为对照眼，左眼为实验眼。制备2．0mm×1．0mm×0．2mm有锈或无锈中碳铁片，经眶路植入兔左眼后极部巩膜板层内。分别于术前1周及术后1周、2周、1个月、3个月裂隙灯下观察并记录角膜、前房、晶状体、玻璃体及眼底的大体改变，并进行闪光视网膜电图（F—ERG）和闪光视觉诱发电位（F—VEP）检查，观察视网膜、视神经的功能变化。3个月实验结束时处死实验兔，观察植入铁片的位置，摘除眼球，行苏木精-伊红染色，光学显微镜下对视网膜、视神经进行组织病理学检查。结果暗适应下F—ERG最大混合反应a波振幅不同时间点之间比较差异无统计学意义（F=1．885，P=0．129），不同处理组之间差异亦无统计学意义（F=1．188，P=0．340）；各组不同时间点的F—ERG最大混合反应b波振幅差异无统计学意义（F时间=2．73，P=0．064；F分组=1．114，P=0．367）。F—VEPN，波隐含时（F时间=1．605，P=0．263；F分组=1．556，P=0．314）、P1波隐含时（F时间=2．329，P=0．092；F分组=2．186，P=0．103）不同时间点及不同处理组之间的比较差异均无统计学意义。实验各指标不同时间及不同干预因素间均无交互作用（P〉0．05）。术后1周、2周、1个月、3个月均未观察到兔眼铁质沉着症改变。实验结束时可见巩膜内铁异物被组织包裹、位置稳定，光学显微镜下兔眼视网膜、视神经均未见明显的细胞学改变。结论兔眼后极部巩膜内细小铁异物无论氧化与否，短期内均不会对视网膜及视神经造成严重的功能性或病理性损害。

Background Iron-containing foreign body trapped in the eyeball wall without affecting the opticus occurs occasionally in clinic. Operation always is performed in an attempt to avoid the deposition of rust in different tissues of the eye-balls. However, a few animal experimental studies showed that a small foreign body does not affect the retina and opticus in the period of three months. The question of whether surgery needs to be carried out is worth discussion. Objective The aim of this study was to evaluate the influence of posterior intraseleral iron foreign body on the rabbit retina and opticus. Methods Twelve healthy adult Japan flap-eared white rabbits were randomly divided into two groups. Medium carbon iron with rust or without rust（ size of 2.0 mm×1. 0 mm×0. 2 mm） were implanted into the posterior sclera of the left eye to create the animal model with iron foreign body in the eyeball wall. The cornea, anterior chamber, crystalline lens, vitreous and fundus of the rabbits were observed under a slit lamp microscope 1 week before operation and 1 week, 2 weeks, 1 month and 3 months after operation. Flash electroretinogram（F-ERG） and flash visual evoked potential（F-VEP） were recorded at the time points mentioned above. All the rabbits were sacrificed and the eye balls were extracted at the end of the experiment, and the position of the iron foreign body was determined. The histopathological examinations of the retina and opticus were performed under the light microscope. This experiment complied with the Regulations for the Administration of Affair Concerning Experimental Animals by State Science and Technology Commission. Results There were no statistical differences for the a-wave amplitude of F-ERG among different time points （F = 1. 885, P = 0. 129 ） and different treatment groups （F= 1. 188,P=0.340）,as with the ERG b-wave amplitude（time：F=2.73,P=0.064;group：F= 1. 114,P= 0. 367）. The differences in the lateneies of F-VEP N1-wave were insignificant among the different time points（F= 1.605,P=0.263） as well as various groups（ F= 1. 556,P=0. 314） ,and those of F-VEP P1-wave were not evidently changed（time：F=2. 329,P=0. 092;group：F=2. 186,P=0. 103）. No correlations were seen between the time factor and grouping factor （ P 〉 0.05 ）. There was no apparent siderosis hulbi change during the follow-up duration. No morphological abnormality in the retina and optical nerve was fi）und under the light microscope. At the end of the experiment,intraseleral iron foreign body was wrapped hy surrounding tissue in a stable condition. Conclusions The small posterior intrascleral iron foreign body,whether it is oxidized or not, does not produce distinctive functional or pathological damage on retina and opticus in the short term.