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Min Wang, Frank Schaeffel, Marita P Feldkaemper; Effects of spectral composition of light on dopamine release and myopia development in chicks. Invest. Ophthalmol. Vis. Sci. 2018;59(9):686. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Different from monkeys, which develop hyperopia in red light, chicks become slightly more myopic in red and more hyperopic in blue light. There is ample evidence that dopamine (DA) is involved in the signaling cascade that controls eye growth by vision but it is unknown how DA release is triggered by light of different wavelengths. Therefore, we studied dopamine release and refractive development in control and deprived eyes in chicks exposed to light of different wavelengths.
Experiment1: Chicks were either kept in the dark, white light, or light emitted by blue (470nm), red (620nm) or UV (375nm) LEDs (all brightness-matched according to the chicken spectral sensitivity function) for 30min. Right eyes were covered with black plastic shields and served as controls. Experiment2: Chicks were kept either under white, or light emitted by UV (375nm), blue (465nm) or red (620nm) LEDs for 5 days. One eye was covered with a diffuser. Refraction was measured daily. DA and its metabolites 3,4-Dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were measured using HPLC-ED at the end of both experiments.
Experiment1: Compared to the dark, DA and DOPAC were clearly enhanced after 30 min in bright light. Also red, blue and UV light exposed eyes had increased vitreal DOPAC levels compared to eyes with black shields (black vs blue: 1.31±0.64vs1.70±0.74; red: 1.26±0.66 vs1.64±0.76; UV: 1.13±0.37 vs1.63±0.41 ng/0.1g wet weight, all p<0.01, paired t-tests). And retinal DA levels were significantly elevated after UV and blue light exposure. Experiment2: Chicks developed significantly less deprivation myopia and had shorter eyes after 5 days exposure to UV and blue light, compared to chicks reared under red and white light. In line with these findings, the amount of vitreal HVA, another measure of retinal DA release, was highest under UV and blue light.
Red, blue and UV light all stimulate release of retinal DA in chicks already after short exposure time of 30 min. Different from humans, chicks have excellent UV vision with a UV cone at 375nm and ocular media that transmit 80-90 percent of light at these wavelengths. This is definitely different from humans where UV below 400nm is largely blocked. Exposure to UV and blue light for 5 days stimulates more DA release than white and red light. UV and blue also inhibit experimentally induced myopia more than white and red light .
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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