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Natalia Ziolkowska, Waldemar Sienkiewicz, Hubert Ziolkowski, Bogdan Lewczuk; Exposure to blue light decreases the number of melanopsin-expressing retinal ganglion cells and nerve fibers in rats. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5255.
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© ARVO (1962-2015); The Authors (2016-present)
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.
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.
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).
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.
Confocal micrographs of M+RGCs in rat retinas. A) control, and B) acute and C) long-term blue-light exposition
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