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

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 intrascleral 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 latencies 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 bulbi change during the follow-up duration. No morphological abnormality in the retina and optical nerve was found under the light microscope. At the end of the experiment,intrascleral iron foreign body was wrapped by 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. Key words: Eye injury ;  Scleral/foreign body;  Visual electrophysiology ;  Visual function ;  Pathology