Elevated Intraocular Hypertension Rat Model By Injecting Compound Carbomer Suspension Into Anterior Chamber

Objective: To establish a stable,repeatable and inexpensive rat model of high intraocular pressure(IOP)by injecting 0.5% compound carbomer suspension into the anterior chamber of SD rats.Morphological changes of retina,anterior segment changes and electroretinogram were observed in carbomer induced rat model.Methods: Forty SD rats weighing 250-300 g(half male and half female)were selected.The right eye was chosen as the experimental eye and the left eye served as control.The basic IOP was measured every morning and every evening three days before operation.0.5%carbomer and 10% sodium hydroxide were used to neutralize the pH for 7.3 to 7.5.A 30 G needle was used to connect the syringe.After intraperitoneal anesthesia,30 ml carbomer suspension was injected into the anterior chamber of rats.At the end of the operation,antibiotic eye ointment was applied.Anterior segment photography was taken every weekend.After ERG examination,10 rats were sacrificed.The eyeballs were fixed in polyformaldehyde solution and embedded in paraffin.The morphological changes of retina were observed by HE staining,and the apoptosis of retinal cells was observed by TUNEL staining.Results: Before injection,the IOP of the experimental eyes was 11.10±0.90 mmHg during daytime and 11.92±1.07 mmHg at night,respectively.The IOP of the control eye was 11.22± 1.07 mmHg during the day and 11.76+1.08 mmHg at night.There was no significant difference between the experimental eye and the control eye during the day and night(P >0.05).There were significant differences between daytime and night in experimental eyes and between daytime and night in control eyes(P < 0.05).There was significant difference in the mean night intraocular pressure between the experimental eyes and the control eyes from the 1st day to the 27 th day after injection(P < 0.05).The morphology of all layers of the retina changed,the thickness of the whole retinal cell decreased,the thickness of the inner plexiform layer(IPL)decreased,the inner and outer nuclear layer(ONL)fused into one,the arrangement of cells was disordered,and the number of ganglion cells decreased significantly.Comparing HE staining of rat eyes at different weeks,it was found that the anterior chamber of the experimental eye contained a mixture of carbomer and iris,which adhered to the corneal endothelium and extended to the angle of the chamber and blocked the trabecular meshwork structure.The angle of the control eye was normal.Compared with the control eyes,the retinal thickness of the experimental eyes became thinner,the number of ganglion cell layer(RGC)decreased,and the amplitudes and amplitudes of a and B waves of electroretinogram(EGR)decreased after 2weeks of intraocular pressure maintenance(P<0.05).TNUEL staining showed positive cells in ganglion cell layer at 2 weeks.Conclusion:Intraocular hypertension model established by anterior chamber injection of carbomer can maintain moderate elevated IOP for more than 4 weeks.The difference between daytime and nighttime IOP is obvious.The intraocular pressure at night is higher than that at daytime,and retinal injury can occur after 2 weeks.Carbomer-induced increased IOP appears to be a viable means for future investigations of mechanisms of glaucoma..The effect of maintaining moderate intraocular hypertension is more than 4 weeks.The difference between day and night is obvious.The IOP at night is higher than that during the day,and the pressure-induced retina damage was found in the HE staining.