| Background and purpose: Scleral encircling operation(SEO) is one of the most important operations in curing complicated retinal detachment. However, as encircling band may affect ocular hemodynamics, aqueous humor dynamics and eyeball structure, which could break the balance of formation and outflow of aqueous humor, secondary glaucoma becomes one of the most popular complications. By establishing animal model of simple scleral encircling in rabbit eyes,and observing changes of intraocular pressure(IOP), as well as pathological changes of anterior segment and retina. Our study aims to explore the effects of simple scleral encircling operation on conventional outflow route and uveoscleral outflow(Fu) of rabbit eyes, as well as roles of Fu in pathogenesis of secondary glaucoma(SG) following scleral encircling operation, so as to seek the range of endurance with the shortening of encircling band in rabbit eyes, and provide experimental foundation for clinical therapy and study.Methods: The rabbits were randomly divided into SEO group and CO(control object) group. SEO group was then divided into five groups according to the shortening of encircling band, of which each one was observed at six time points: ld,3d,lw,2w,4w and 8w. IOP was measured using direct ophthalmotonomete. Haematoxylin-eosin staining specimens were observed with light microscope. So as for pathological changes of angle of anterior chamber, trabecular meshwork, ciliary body, choroids, retinal ganglion cell (RGC) and layer of optic fibers. TUNEL technology was used to determineapoptosis of RGCs. Value of uveoscleral outflow was measure with FITC-Dextran as labeled tracer. Results:I. Compared with that in CO group, IOP elevated respectively in each one of the five SEO groups. There was a positive correlation between the level of IOP elevation and volume of encircling band shortening.II. Value of uveoscleral outflow elevated respectively in all five SEO groups at different levels. It reaches peak at 3d,which was three times higher than the basic volume.III. Few TUNEL positive cells were found in retina of rabbit in CO group. Compare with CO group, there were more TUNEL positive cells in the retina of rabbit after operation, and the rate of TUNEL positive cells was found increase to the highest level at the point of Iw after operation. There was a positive correlation between the rate of TUNEL positive cells and volume of encircling band shortening.IV. Depth of anterior chamber became shallow little by little with increasing shortening volume of encircling band. Ciliary body and trabecular meshwork edema appeared during earlier period of post-operation. Fibrosis of trabecular meshwork was observed in group II~V at the point of 2w after operation,and change was more distinct with increasing shortening volume of encircling band. Few detachment of choroids and ciliary body was found in group I and II and that was more in group III ~ V. One week after operation, vacuolation in retinal nerve fiber layer appeared in group II~V, and retinal ganglion cell (RGC) reduced.Conclusions:I. Little change was found with angle of anterior chamber and trabecular meshwork in group 5% ~15%,and elevated IOP recovered with increasing of Fu and Extinction of inflammation. Severe pathologic change of angle ofanterior chamber and trabecular meshwork was found in group 20% and 25%,and permanent lesion of anterior segment ischemia appeared in some cases.II. Sudden decrease of volume of eyeball contributes to immediate elevation of IOP. It was ciliary body edema, ciliary body detachment, choroids detachment, subchoroid hemorrhage and following changes of trabecular meshwork that was the principal mechanism of secondary glaucoma after SEO.III. Delayed retina ganglion cell death occurred in group II~V.The main mechanism of delayed RGC death is apoptosis. It reaches a boom Iw after operation.IV.Value of uvoescleral outflow elevation was found in different groups after SEO. The possible mechanism of elevation in...
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