Affiliations: [a] Institute of Health and Biomedical Innovation, Queensland University of Technology (QUT), Brisbane, Australia
| [b] School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, Australia
| [c] Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, Australia
| [d]
Queensland Eye Institute (QEI), Brisbane, Australia
| [e] School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, Australia
| [f] Movement Neuroscience Program, Queensland University of Technology (QUT), Brisbane, Australia
Correspondence:
[*]
Correspondence to: Beatrix Feigl, MD, PhD, Medical Retina Laboratory, Institute of Health and Biomedical Innovation, QUT. 60 Musk Avenue, Kelvin Grove, Queensland 4059, Australia. E-mail: b.feigl@qut.edu.au.
Abstract: Background:Melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) signal the environmental light to mediate circadian photoentrainment and sleep-wake cycles. There is high prevalence of circadian and sleep disruption in people with Parkinson’s disease, however the underlying mechanisms of these symptoms are not clear. Objective:Based on recent evidence of anatomical and functional loss of melanopsin ganglion cells in Parkinson’s disease, we evaluate the link between melanopsin function, circadian, and sleep behavior. Methods:The pupil light reflex and melanopsin-mediated post-illumination pupil response were measured using chromatic pupillometry in 30 optimally medicated people with Parkinson’s disease and 29 age-matched healthy controls. Circadian health was determined using dim light melatonin onset, sleep questionnaires, and actigraphy. Ophthalmic examination quantified eye health and optical coherence tomography measured retinal thickness. Results:The melanopsin-mediated post-illumination pupil response amplitudes were significantly reduced in Parkinson’s disease (p < 0.0001) and correlated with poor sleep quality (r2 = 33; p < 0.001) and nerve fiber layer thinning (r2 = 0.40; p < 0.001). People with Parkinson’s disease had significantly poorer sleep quality with higher subjective sleep scores (p < 0.05) and earlier melatonin onset (p = 0.01). Pupil light (outer retinal) response metrics, daily light exposure and outer retinal thickness were similar between the groups (p > 0.05). Conclusion:Our evidence-based data identify a mechanism through which inner retinal ipRGC dysfunction contributes to sleep disruption in Parkinson’s disease in the presence of normal outer retinal (rod-cone photoreceptor) function. Our findings provide a rationale for designing new treatment approaches in Parkinson’s disease through melanopsin photoreceptor-targeted light therapies for improving sleep-wake cycles.
