Objective To investigate the effect of different spectral compositions of light on the release of dopamine by human retinal pigment epithelial (RPE) cells in vitro.Methods Experimental study.Cultured human RPE cells (RPE-19) were exposed to either full spectrum light or red,green,blue (RGB) spectrum light in the intensities of either 4000 lx or 1000 lx.Cells exposed to no light irradiation were used as the control.Cells were assayed at 24 hours and 48 hours for the secretion of dopamine using high performance liquid chromatography (HPLC) and cell viability by WST-1 (a sodium salt of 4-[3-4-iodophynyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate assay).Data were analyzed using one-way ANOVA.Results There was no statistical significance in the difference of proliferation rates between the full spectrum group and the RGB group at 1000 lx for the first 24 hours,while the difference was statistically significant at the 4000 lx level (P＜0.05).In contrast,full spectrum light significantly suppressed the proliferation of cells compared to RGB light at 48 hours,both in the low and high light intensities (both P＜0.01).After 24 hours treatment,the difference in the concentration of dopamine was not significant between the full spectrum group and the RGB group at an intensity of 1000 lx,while the difference was statistically significant at 4000 lx (P＜0.01).Furthermore,the concentration of dopamine at 48 hours was higher in the full spectrum groups than in the RGB groups at both intensity levels (both P＜0.05).Conclusion The present study found that the spectral composition of light is involved in regulating the release of dopamine by RPE and the effect was closely correlated with light intensity and time.These results demonstrate the importance of considering spectral composition when investigating sunlight's protective effect against the development of myopia.