Abstract： Objective To investigate the relationship between exposure intensity and illumination time of blue light and replicative senescence of rat retinal pigment epithelial (RPE) ceils.Methods Thirty-six 12-14 weeks Wistar rats were kept in the cage with a blue-light bulb [(450±10) nm],and were randomly divided into four groups (no light,nature light,500 lx light and 1000 lx light illumination),each has nine rats.The rats in each group were further divided into three subgroups according to illumination time (one month,two months or three months).Eyeballs were collected after intraperitoneal injection of 10% chloral hydrate.The right eye of each rat was embedded in paraffin and sectioned for hematoxylin-eosin (HE)staining,while frozen sections of the left eye were stained for the senescence-associated β-galactosidase (SA-β-Gal).The data were analyzed by SPSS11.5 statistical software.Results The amounts of SA-β-Gal positive RPE cells were significantly different between all groups under the same illumination time 17 (P=0.000),and between all subgroups of different illumination time with same exposure intensity (P＜0.01)except for the control group (no light).Conclusion Blue-light can induce replicative senescence in rat RPE cells in an intensity and time-dependent manner.