Sleep disturbances, such as insomnia, sleep fragmentation, excessive daytime sleepiness, and REM sleep behavior disorder are common in people with Parkinson's disease (PD). Poor sleep quality can also impact other domains of function, including motor function. Prior research has shown that a type of photoreceptor cell in the retina, called melanopsin cells, provide the main light signals to the brain to initiate sleep, and function of these cells is impaired in PD. Dr. Beatix Feigl and her colleagues developed a novel light therapy intervention that selectively activates the melanopsin photoreceptor cells, and in this episode, she discusses the results of a recent randomized controlled trial evaluating the efficacy of this melanopsin photoreceptor-directed light therapy on sleep and circadian rhythm, as well as motor behaviors. She also discusses her earlier work on melanopsin cells that led to the development of standard measures to assess their function. Beatrix is an Ophthalmologist and an Associate Professor in the School of Biomedical Sciences and Center for Vision and Eye Research, as well as the Faculty of Health, at the Queensland University of Technology. This podcast is geared toward researchers and clinicians. If you live with Parkinson’s or have a friend or family member with PD, listen to The Michael J. Fox Foundation Parkinson’s Podcast. Hear from scientists, doctors and people with Parkinson's on different aspects of life with the disease as well as research toward treatment breakthroughs at https://www.michaeljfox.org/podcasts.