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为探讨眼内铁磁性异物ＭＲＩ时的移动性，对９枚铁屑（０．２ｍｍ×０．２ｍｍ×０．１ｍｍ～４ｍｍ×３ｍｍ×３ｍｍ）进行了体外实验，对１０枚铁屑（０．２ｍｍ×０．１ｍｍ×０．１ｍｍ～３．５ｍｍ×３ｍｍ×３ｍｍ）进行了体内实验。体外实验将铁屑放入盛有兔眼玻璃体的透明玻璃瓶中，体内实验将异物置入５只兔的１０眼玻璃体内。ＭＲＩ使用ＳｉｅｍｅｎｓＩｍｐａｃｔ１．０ＴＭＲ机。体内实验ＭＲＩ前后经检眼镜和ＣＴ观察异物移动情况，并拍摄Ｘ线平片。结果：体外实验发现仅１枚最小铁屑（０．２ｍｍ×０．２ｍｍ×０．１ｍｍ）未见移动，其他８枚均见异物向主磁场方向移动。体内实验３枚小于０．３ｍｍ×０．３ｍｍ×０．２ｍｍ铁屑未见移动，大于０．４ｍｍ×０．３ｍｍ×０．２ｍｍ的７枚铁屑均见移动，但并未导致视网膜损伤。ＭＲＩ均发现铁异物周围有大于异物数十倍的金属伪迹；小于０．４ｍｍ×０．３ｍｍ×０．２ｍｍ的４枚铁屑Ｘ线平片均未显示。结果提示：眼内铁磁性异物移动性与异物大小有关，异物愈大愈易移动；Ｘ线平片不能显示的眼内铁异物在１．０ＴＭＲ机下行ＭＲＩ是安全的
In order to investigate the mobility of intraocular ferromagnetic foreign bodies during MRI, 9 iron filings (0.2mm × 0.2mm × 0.1mm ~ 4mm × 3mm × 3mm) were tested in vitro. 2 mm × 0.1 mm × 0.1 mm to 3.5 mm × 3 mm × 3 mm). In vitro experiments Iron filings were placed in a clear glass bottle containing vitreous of rabbit eyes. In vivo experiments, foreign bodies were placed in 10 eyes of 5 rabbits. MRI using SiemensImpact1.0TMR machine. In vivo experiments before and after the operation of glasses and CT examination of foreign body movement and X-ray film. Results: In vitro experiments showed that only a minimum of iron filings (0.2 mm × 0.2 mm × 0.1 mm) were not seen, and the other 8 were all seen to move toward the main magnetic field. In vivo experiments, three pieces of iron chips smaller than 0.3mm × 0.3mm × 0.2mm did not move, and more than 0.4mm × 0.3mm × 0.2mm 7 iron chips were seen moving, but did not cause retinal damage. MRI found that there are metal artifacts around the foreign body than the number of foreign objects dozens of times; less than 0.4mm × 0.3mm × 0.2mm 4 iron X-ray films are not shown. The results suggest that the mobility of intraocular ferromagnetic foreign body is related to the size of the foreign body, and the larger the foreign body is, the easier it is to move. The intraocular foreign body foreign body that can not be displayed by X-ray film is safe