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Lisa A Ostrin, Kaleb Abbott, Hope M Queener; Modulating ipRGC Input to Improve Sleep and Regulate Circadian Rhythm. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4665.
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© ARVO (1962-2015); The Authors (2016-present)
The intrinsically photosensitive retinal ganglion cells (ipRGCs) are linked to various aspects of circadian rhythm through short wavelength blue light stimulation via the retinohypothalamic tract and ultimately to the pineal gland. This study sought to investigate whether melatonin levels and sleep quality can be modulated by manipulating input to the ipRGCs.
Adult subjects (ages 18-42, n=17) wore amber tinted glasses (blocking wavelengths <550 nm) from sunset to bedtime for two weeks. The ipRGC response was measured at baseline and after two weeks by analyzing the relative post illumination pupil response (PIPR) at 6s following 1s stimulation 456 nm light. The ipRGC responses were measured before 11:30 am in all cases. Subjects answered the Pittsburgh Sleep Quality Index (PSQI) survey at two time points, and wore an actigraph device (Actiwatch Spectrum) one week prior and during the experimental period for objective measurements of activity, light exposure, and various sleep parameters. In addition, saliva samples were collected for melatonin analysis at nighttime and morning before and after glasses wear.
The ipRGC mediated PIPR showed a slower redilation phase as indicated by the significantly smaller relative pupil diameter 6s following light offset (p<0.05) after two weeks of glasses wear, indicating an increase in activity of ipRGCs in the morning. The subjective PSQI score improved from 5.1±3.3 to 2.9±2.5. Night time melatonin levels increased from 18.6±8.7 pg/ml to 24.8±11.8 pg/ml (p<0.05) and morning melatonin levels decreased from 6.93 pg/ml to 5.5 pg/ml (p=0.005). Objective sleep analysis showed a significant increase in sleep duration of 22.2 minutes, from 7:01 hrs:min to 7:23 hrs:min (p=0.01). There was not a significant correlation between the PIPR and melatonin levels.
The use of blue-blocking glasses increased subjectively measured sleep quality and objectively measured sleep duration, presumably as a result of decreased blue light input to the ipRGCs. While melatonin and ipRGC responses were both altered, the lack of association between them may be due to phase shifts in peak activity of the two processes. Results suggest that minimizing artificial light following sunset may help in regulating circadian rhythms.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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