Photodynamic Method Preparation Of Nonarteritic Ischemic Optic Neuropathy Of Rats Model

Objective：Nonarteritic anterior ischemic optic neuropathy (NAION) is acommon optic neuropathy seriously affecting the visual function in themiddle-aged and elderly population. At present, its pathogenesis is notcompletely clear. In recent years, scholars of ophthalmology put forward manytreatment methods for NAION, but its treating efficacy is dissatisfactory.Therefore the current study on NAION is focused on the establishment ofsuitable animal model and the pathogenesis. The rat model of NAION(rNAION) by photodynamic method based on the pathophysiology andpathogenesis similar to human NAION, for further study of the pathogenesis,provides research foundation for clinical prevention and treatment programs.Methods：40SD rats were randomly divided into4groups, grouprNAION with25rats, group laser with5rats, group photosensitizer with5rats,group control with5rats, each group of random numbers. All of the right eyeswere the experimental eyes and the left ones were the control. Afteradministration of Rose Bengal(rose Bengal, RB)2.5mmol/(l·kg) in rats’ tailvein, the rat ON was directly treated with an green532-nm, power75mW/500-μm spot laser/2/3disc spot laser for18seconds in group rNAION,the rats in group laser were treated with the green532nm, power75mW/500-μm spot laser/2/3disc spot laser for18seconds，the rats in groupphotosensitizer were treated by administration of Rose Bengal(rose Bengal,RB)2.5mmol/(l·kg) in rats’ tail vein, the rats in group control were not treated.Using fundus fluorescein angiography(FFA)，histologic，electrophysiologicalmethods, to observe and record retinal vascular filling process and optic discedema before induction and1,3,5,7,14,21,28days after induction; for flashvisual evoked potential(F-VEP) before induction and1,7,14,21,28days afterinduction, and the rats were sacrificed at each time point. Selecting the optic nerve and retinal tissues were observed by HE staining and scanning electronmicroscope.Results：From1day to5days after rNAION induction，the optic discwas pale and swollen in the superior part, and subsided in the7th day. Theoptic disc at28days after induction was pale and shrunken. In early FFA，hypofluorescence appeared at the ischemic area of the optic disc, and in midstand later stage the superior part revealed hyperfluorescence in the1st day afterrAION induetion; Seventh day after rAION model, the hypofluorescenceappeared in the ischemic area of the optic disc in midst and later stage, and thehypofluorescence in the28th day. The optic disc and peripapillary retinaledema in the1st day after rAION induction; the surface of optic disc showedlower than the surface of retina in the28th day after rNAION induction inOCT. The latent period of F-VEP expanded，the amplitude cut down in the lday after rNAION induction and did not changed in28days. After fixationand hematoxylin-eosin staining of4-μm sections，in high power field the opticdisc and peripapillary retinal nerve fiber layer showed edema1day aftertreatment. From7days to21days after rNAION induction，the edema of opticdisc and peripapillary retinal nerve fiber layer had resolved with the number ofretinal ganglion cells were decreased, and the arrangement of nuclei withininner nuclear layer was disordered. Rarefaction and degeneration in the nervefiber of retina and reduction of the number of nuclei of ganglion cells in the28st day after the model induction，and the thinning of nerve fiber of the opticdisc and its surroundings. The inner nuclear layer disordered arrangement ofthe nucleus, mildly thinning. One day after treatment, under electronmicroscope，peripapillary retinal ganglion cell volume become bigger, nuclearvacuole degeneration, mitochondria vacuolar degeneration and endoplasmic.There were visible edema in the inner nuclear layer and the inner plexiformlayer. The observations were retinal ganglion cell nucleus pycnosis, nuclearmembrane dissolved and the golgi apparatus expended in the28st day after themodel induction. In contrast，there was no change in group control，group laserand group photosensitizer. Conclusion：Photodynamic method combined with rose bengal dye is asimple，reliable and definitive experimental technique to produce rats NAIONmodel．Furthermore, this study can be evaluated drugs which are using theNAION and proposed new treatment options.