Effect of blue light exposure on number of melanopsin positive intrinsically photosensitive retinal ganglion cells (ipRGCs) in whole-mount retinas from Wistar rats. The rats were exposed to 12 h white light (150 lx) and 12 h darkness for 10 d (control, CTRL; 9 rats), cycles of 12 h blue light (150 lx) and 12 h darkness for 10 d (long-term exposure, LTE; 9 rats), and constant blue light (150 lx) for 2 d (short-term exposure, STE; 9 rats). (A) Circles show number of melanopsin positive ipRGCs in a whole-mount retina from one rat. Horizontal lines show 20%-trimmed mean. (B) Dot shows difference between group means. Error bar shows 95% confidence interval for the difference. p-values and confidence intervals were calculated with Wilcox’s robust technique based on trimmed means [34,35].