| Objective:To observe the retinal morphology changes and the effect of endothelin-1 afterintravitreous injection with dexamethasone for retinal edema which was induced by argon laserin rabbit eyes, we explored dexamethasone to the therapy effect of retinal edema and possiblemechanism.Methods:Forty healthy pigmented rabbits were randomly divided into group A (balance saltsolution control group), group B (DEX intervention group). Group A and group B respectivelyaccording to different killing time were divided into four groups, 12h,1d,3d and 5d after thetreatment, each subgroup had five rabbits. The model of retinal edema was established withargon laser photocoagulation to retinal vein in right eyes of fourty healthy pigmented rabbitsand the forty left eyes of rabbits do nothing as normal control group. The twenty right eyes ofgroup A were intravitreally injected with balance salt solution 0.2ml and the twenty right eyesof group B were intravitreally injected with dexamethasone 1mg / 0.2ml. Intraocular pressure(IOP) and optical coherence tomography (OCT) was performed on each animal before and afterintravitreous injection. After the examination the animal was killed and the eyeballs wereextirpated at the four points of time after the injection. The ultrastructural changes of the retinaand the expressions of ET-1 were observed by light microscopy through HE dyeing andimmunohistochemical staining SABC methods which were quantized by image analysis system.All the datum were analysised by ANOVA of SPSS software.The results:1. The models of retina edema were successfully established in forty pigmented rabbits.2. IOP check: The IOP of the control group and DEX intervention group were generally nosignificant difference (P > 0.05). The IOP of two groups were no significant difference on12 hour, 1 day, 3 day and 5 day after the injection (P > 0.05). The change trend of IOP wasalmost the same over time in two group (P > 0.05).3. OCT check:The retinal thickness of DEX intervention group was significantly less thanthat saline control group on 12 hour, 1 day, 3 day and 5 day after the intravitreous injection(P < 0.05). The change trend of retinal thickness was inconsistency over time in balance saltcontrol group and DEX intervention group (P < 0.05). The retinal thickness reducedgradually after intravitreous injecting DEX, however, the retinal thickness increasedgradually in saline control group. The retinal thickness after injection 12h respectively with after injection 3d, 5d was statistically significant compared difference (P < 0.05).4. Histopathologic observation: The normal retina showed clear structure and no degenerationof retinal tissues. The retinal structure in saline control group disordered while retinalganglion cells and parts of inner and outer nuclear layers were swollen on 12 hour aftertreatment; The number of retinal ganglion cells reduce even vanished and externalplexiform layer cells were swollen and the segments of inner and outer nuclear layersbecame collapsed on 1 day; The retinal structure was not clear and fiber proliferated on thesurface of the inner limited membrane on 3 day; The retinal structure of 3 day aftertreatment was equal with 3 day after treatment. The retinal structure of 12 hour in DEXintervention group was similar with 3 day in saline control group; A little of retinal ganglioncells were vacuolated and a little of inner and outer nuclear layers vanished on 1 day;Retinal ganglion cells did not see obvious abnormity and a little of external plexiform layercells were swollen on 3 day; The retinal structure was more clear than saline control groupon 5 day after treatment.5. ET-1 expression in retinal:The expression of ET-1 had expressed on 12 hour after treatment.The expression of ET-1 in DEX intervention group was significantly less than that salinecontrol group on 12 hour, 1 day, 3 day and 5 day after the intravitreous injection (P < 0.05).The change trend of expression level of ET-1 was inconsistency over time in balance saltcontrol group and DEX intervention group (P < 0.05). The expressions of ET-1 increasedgradually in saline control group, especially on 3 day and 5 day after injection, however, theexpressions of ET-1 reduced gradually after intravitreous injecting DEX and the declinetrend was slowing. Statistically significant compared difference (P < 0.05).ConclusioConclusion:DEX could effectively fast reduce retinal edema through restraining the ET-1from secretion and liberation in short time.
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