An improved model of light-induced retinal damage for grading standardization in rat

Abstract

Background Light-induced retinal damage models vary as many influence factors,herein the modeling method is difficult to copy.It is necessary to establish the grading standardization of retinal damage after retinal light exposure.Objective This study was to improve the modeling method and establish a grading standardization for light-induced retinal damage in rat.Methods Twenty-four SPF 8-10 week-old male SD rats were randomly divided into 4 groups and 6 eyes for each group.The rats were exposed to light intense of 5000 lx for 1,2,3 hours respectively in 3 groups,and other 6 rats served as the normal group.Full-field light exposure experiment was performed for each individual rat separately,and an annular illumination box was used tO ensure the experimental rat moving in a single direction and exposing the right eye in 5000 lx light surrounding during experimental duration.Ganzfeid electroretinogram(ERG)was recorded from the experimental rats at the fifth day after light exposure,and the animals were then sacrificed for histopathology observation to evaluate the retinal thickness change.All procedures which involved animals adhered to the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research.Results After exposing to intensity light for 1,2,3 hours,the b-wave amplitudes of rod response,maximal mixed response,oscillatory potential in scotopic ERG as well as cone response,20 Hz flicker response of photopic ERG were significant declined as lapse of light exposure time(F=71.690,P=0.000；F=56.250,P=0.000；F=23.610,P=0.000：F=27.130,P=0.000；F=27.030,P=0.000)and lowed by 26.2％,52.5％,70.7％,24.4％,39.3％,58.1％respectively at the end of experiment.Meanwhile,the b-wave latencies of rod response,maximal mixed response in scotopic ERG as well as cone response of photopic ERG were evidently different among different groups (F=1.370,P=0.282；F：0.800,P=0.508；F=11.840,P=0.000；F=2.080,P=0.136).Light induced retinal damage located mainly at the temporal retina area.After intensity light exposure for 1,2,3 hours,the thickness of outer nuclear layer at the superior temporal retina attenuated by 11.3％,25.6％and 72.5％,respectively(P<0.05).A significant difference was seen in mean thickness of outer nuclear layer at superior temporal retina among different groups(F=410.27,P=0.000). Conclusion A standardized grading method for light-induced retinal damage is recommended.The continuous illumination in a intensity of 5000 Ix for 1,2,3 hours can induce the mild,moderate or severe retinal damage respectively at temporal retina. Key words: Rat; Light induced retinal damage; Animal model; Standardization of grading