Morphometric Study Of The Retina In The Rat Eye With Glaucoma Induced By Laser Photocoagulation Of The Trabecular Meshwork

Purpose: To characterize the regularity of intraocular pressure inglaucoma rat model induced by laser photocoagulation of trabecularmeshwork, and the morphological quantitative analysis of retina by means ofstereology method.Methods: A total of40healthy wistar rats aging2months were dividedinto a photocoagulation group and a blank control group. In photocoagulationgroup, one eye (alternating right and left eye) in each rat was treated by laserphotocoagulation and the contralateral eye served as its own control.Altogether for4times at a7-day interval, IOP was measured in both eyesbefore laser coagulation, the moment of accomplished photocoagulation andthe same time of6days weekly for4weeks after photocoagulation. after onemonth randomly chosed half of the survival as the4weeks group andgathered the both eyeballs with the optic nerve under general anesthesia; theother as the8weeks group measured IOP for one more month and gatheredthe both eyeballs with the optic nerve under general anesthesia after twomonths. the blank group gathered the both eyeballs on the same time with the4weeks group. These eyeball tissues did resin embedding and slicedrespectively, after HE ataining, observed the change of the trabecularmeshwork under light microscope, measured the retinal ganglion cell layerthickness and counted retinal ganglion cells with stereology method.Results: IOP in the rats was15±3.8mmHg before the first laser treatment, and increased to24±6.3mmHg at the moment of accomplishedphotocoagulation（t=6.632,P<0.05）；The highest mean IOP was available onthe first day after photocoagulation, then began to decrease in succession andbe normal on the sixth day. The change of IOP showed the same regularityafter each repeat photocoagulation. The morphological change showed thatthe trabecular meshwork of experimental eye compression, narrow down,even some shutting, disappear; the trabecular cells was reduced; some parts ofiris was curled, edema, thickening, appeared obvious anomalies. Themeasurement results by stereology method showed that the ganglion cellslayer thickness of the experimental eye of4weeks group was76.9±8.3μm,theganglion cells layer thickness of the contralateral eye was94.3±9.7μm, Thedifference was statistically significant（t=-4.887,P<0.05）; the ganglion cellslayer thickness of the experimental eye of8weeks group was86.2±13.3μm,the ganglion cells layer thickness of the contralateral eye was99.8±9.9μm, The difference was statistically significan（tt=-4.981,P<0.05）. Inthe4weeks group, the RGCs average density of experimental eye was(3.97±0.77)×103×mm-2, the RGCs average density of contralateral eye was(5.68±1.63)×103×mm-2, the experimental eye was obviously decreased by24.7%compared with the contralateral eye（t=-2.54,P<0.05）. In the8weeksgroup, the RGCs average density of experimental eye was(3.39±0.82)×103×mm-2, the RGCs average density of contralateral eye was(4.96±0.98)×103×mm-2, the experimental eye was obviously decreased by31%compared with the contralateral eye（t=-6.608,P<0.05）.During theprocess of measuring,we found two tissue sections of4weeks group showedthat the tissue severely damaged,trabecular meshwork and retinashrinked,couldn’t to distinguish between organization,so not measured. Conclusion: It is successful that establish the rat glaucoma model by adiode laser with wavelength of532nm irradiating trabecular meshwork viaexternal limbus. This model leads to transient elevated IOP, chronic glaucomaanimal model can be produced by repeated photocoagulation of trabecularmeshwork with a laser. And the experimental eyes appear glaucoma retinal orretinal optic nerve characteristic morphological changes.It is successful thatthe morphological quantitative analysis of retina by means of stereologymethod.