Abstract
Purpose :
The negative effects of blue light on the retina have drawn attention due to increasing use of devices emitting blue-enriched light. To date, quantitative studies of the effects of exposure to this light on melanopsin-containing retinal ganglion cells (MRGCs) have not been done. Melanopsin (M) is a blue-light sensitive pigment that is expressed in these cells. Thus, the aim of this study was to compare the number of M+RGC bodies and the density of M+ nerve fibers in the retinas of rats exposed to blue light and those kept in natural lighting.
Methods :
Wistar albino rats (3 months old) were used in this study. Rats in the control group (n=6) were exposed to 12 h of daylight and 12 h of darkness for 10 d. Those in the acute exposure group (n=6) were continuously exposed to blue light for 48 h. Rats in the long-term exposure group (n=6) were exposed to 12 h of blue light and 12 h of darkness for 10 d. Blue light was provided by light emitting diodes (460-480 nm, 150 lux). Whole-mount retinas were immunolabelled with melanopsin antibody, then visualized with a confocal microscope (LSM700, Zeiss). To quantify M+RGC bodies, ImageJ 1.51n software was used. The density of M+ nerve fibers was estimated by superimposing a Mertz Grid and counting the intersections between nerve fibers and grid lines on each photograph. For statistical analysis, t-tests with a Bonferroni correction were used.
Results :
There were significantly more M+RGC in the control group than in the groups exposed to blue light (control, 1955 ± 497 (SD); acute, 618 ± 163; long-term, 724 ± 266; control vs. acute, P<0.001; control vs. long-term, P<0.001; acute vs. long-term, P=1.0). Similarly, there were significantly more intersections between nerve fibers and the Mertz Grid in the control group than in the two exposed groups (control, 94 ± 10; acute, 34 ± 2; long-term, 53 ± 15; control vs. acute, P<0.001; control vs. long-term, P<0.001; acute vs. long-term, P=0.03).
Conclusions :
These results indicate that exposure to blue light reduces both the number of MRGC bodies in the rat retina, and the density of M+ nerve fibers in this tissue. Further studies should determine if the decrease in the number of MRGCs is due to down-regulation of M expression or cell-death.
.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.