| Background and Aims With the evolution of modern warfare, eye injuries have increased from 2% during World War I and World War II to 13% in the Persian Gulf War. Among these caeses,about 78% resulted from exploding fragments. Penetrating injuries with associated IOFBs accounted for 31% to 85% and 80-90% were associated with retinal injury. The National Eye Trauma System Registry reported that in an industrial series, penetrating injuries with a retained IOFB accounted for 35% of all the cases, with two thirds of IOFBs located in the posterior segment. The etiology of most retained IOFBs was an isolated metal projectile generated by hammering metal on metal. This kind of ocular trauma caused by flying projectiles often has had a uniformly poor prognosis since the advances of vitreoretinal surgery. The factors influencing the final visual results has been illustrated as the following: initial visual acuity, retinal injuries, vitreous hemorrhage, metallosis bulbi, Proliferative Vitreoretinopathy(PVR), tractional retinal detachment(TRD) and Endophthalmitis. But there was few report about the influence of the globe blood circulation.In this articl we established eye injury model in rabbit with air gun. And observed the changes of the choroid blood vessel volume(Vb) and did the electroretinogram (ERG)of the injuried-eyes. Finally, we proached the relationship between the changes of Vb and ERG.Methods1. Nail gun was used to establish the eye injury model by shotting prepared nail into rabbit's eye. Different air pressures leading to varied traumatic condition were compared respectively. The air pressure which could produce penetrating eye injury with IOFBs involoving retinal injury was considered as the proper air pressure to build the animal model.2. Efforts were made to observe the clinical manifestations of the injuried eyes and count the incidence rate of the retinal detachment(RD) and endopthalmitis within 8 weeks after injury. Histopathologic changes of the injuried-eye enucleated on the 1d, 3d, 1w, 2w, 4w and 8w post-injury were observed.3. There groups were set up to compare the different influence to the visual function with the different factors. Test group consisted of 10 eyes injuried by projectile. The negative control group consisted of 10 eyes that had sharp penetrating injury (6mm long and 2mm from the limbus through the pars plana, avoiding the lens and peripheral retina). The positive control group consisted of 10 eyes that had same sharp penetrating injury as the negative control group, and in addition, a prepared nail was inserted into the vitreous cavity through the sclera incision.ERG was used to evaluate the visual function post injury in these three groups.4. The clinicopathological slides of the eyes enucleated on the 1d, 3d, 1w, 2w and 4w after injury were examined. The choroid volume(Vc), blood vessel density of choroid (Vv) , blood vessel volume of choroid (Vb) were measured by stereological methods.5. Pearson correlation method was used to explain the relationship of the changes of Vb and the amplitude of a-wave and b-wave.Results1. The clinical manifestations of the injured eyes got worse with the increase of the damaging air pressure. When air pressure was 6kg/cm2, among the injuried-eyes, about 83.3% produced retinal injury, which often occured to clinic patients. The incidence rate of the RD was 22%, endopthalmitis was 6% in 8 weeks after injury. The histopathologic changes of the model were also close to clinic eye injuries.2. The results of the ERG show that compared with pre-trauma, the amplitude of max a-wave and b-wave were both significantly reduced on the 1d post-trauma(P<0.01), and then recovered on the 3d in the negative control group. In the positive control group, the amplitude of a-wave and b-wave were all significantly lower than pre-trauma through all time post-trauma(P<0.01), and the test group was more lower than the positive control group(P<0.05).But the later two groups had the same trace of changes: the amplitude of a-wave on the 3d-2w were at a stable low value, and then persistently went down after 2w.The amplitude of b-wave on the 3d-2w were elevate, and then persistently went down after 2w as the a-wave. 3. Compared with normal choroid , the Vc, Vv and Vb of traumatic eyes in the positive control group were all significantly reduced on the 1d after jinjury(P<0.01), and then recovered on the 1w(P>0.05). The result of the test group was different from that of the positive control group, the Vv and Vb were both significantly reduced on the 1d after jinjury(P<0.01),and then contiune to go down, at the lowest level on the 3d post trauma, and 1w-4w elevate gradually, but even on the 4w could not recover to the normal value. The Vc significantly reduced in the all time(P<0.01)and had no significant changes between the times post trauma(P>0.05).4. The changes of Vb in test group of injuried eyes had significant correlation with the changes of the max a-wave and b-wave(a-wave P<0.05, b-wave P<0.01). But in the positive control group,there was no correlation between the changes(P>0.05).Conclusions1. A comparatively ideal model of eye injury caused by projectiles could be established with the nail gun. The changing air pressure could lead to various injuries. And the wound location could be definite. 6kg/cm2 was the air pressure possibly causing injury to clinic patients.2. The pure sclear sharp penetrating injury near the limbus had little influence to the final visual outcome. The metal foreign body retained in globe had severe harm to the visual function. Its early remove would be good to the final visual outcome. The eye injury caused by projuectiles has poor visual prognosis. Pressure wave was one of the important factors to infulence the final vision.3. The choroid damage in the injuried eyes caused by projiectile was severe. The reducing of the Vb would lead to the reduction of the globe blood circulation, and then influence the visual function. So it is important to enhance the treatment to improve the vessle function after eye injury by projectiles. |
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