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Baskar Arumugam, Li-Fang Hung, Lisa A Ostrin, Zhihui She, Earl L Smith; Effects of Long-Wavelength Lighting on Activity Patterns and the Pupil in Infant Rhesus Monkeys. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5043. doi: https://doi.org/.
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Our aim was to determine whether quasi-monochromatic long-wavelength light rearing affects activity patterns and ipRGC driven pupil responses in infant rhesus monkeys.
Infant monkeys were reared under long-wavelength (630 nm; 274±64 lux) LED (LWL, n=11) or fluorescent lights (FL; 559±235 lux, n=6) on a 12 hour light/dark cycle from 21 to 150 days of age. Animals were fitted with an activity and sleep tracker (Fitbit Flex). Pupil diameter was measured photographically during the lights-on period at various points during the rearing period. At the end of the rearing period, rod/cone and ipRGC driven pupil responses to 1 second(s) long- (133 cd/m2) and short-wavelength lights were assessed through post illumination pupil response (PIPR); metrics included the relative 6s and 30s PIPRs, early area under the curve (AUC), and late AUC.
During the early rearing period, the LWL-reared animals showed significantly higher percentages of active time during the lights-off cycle compared to the FL-reared animals (2.89% vs 0.99%, p=0.001) and the average activity counts were higher for LWL than FL animals during the lights-off cycle (relative counts: 0.81±0.37 vs 0.27±0.15, p=0.001). There were no significant differences in activity during the lights-on period (relative counts: 26.78±9.10 vs 26.77±9.77; p=1.0). Near the end of the rearing period, there were no significant differences between the LWL- and FL-reared monkeys in the percent-active time during lights-off (1.44% vs 1.07%) and lights-on (98.56% vs 98.93%, p=0.44) periods. The pupil diameter for the LWL monkeys was significantly larger than for FL animals (4.8±0.5mm vs 3.8±0.4mm, p=0.0001). All PIPR metrics were attenuated in LWL-reared animals compared to FL animals; however, these differences did not reach statistical significance. For example, for the 16 cd/m2 short-wavelength light, the 6s PIPR and early AUC in LWL animals was 0.85±0.09 and 1.57±0.79 and in FL animals was 0.79±0.09 and 2.08±0.76 (p=0.08 and 0.09), respectively.
Monochromatic long-wavelength lighting initially resulted in alertness at night during the early rearing period in infant monkeys. These results suggest that complete elimination of short-wavelength light can potentially interfere with circadian rhythms. Normal activity and pupil responses at the end of the experimental period suggest that at least some aspects of the circadian system adapted.
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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