This study looks at how *light therapy*, a treatment using bright light, can help people with **Parkinson's disease** (PD) with their movement and sleep problems. In this study, light therapy is tested to see if it helps people move better and sleep better. **Parkinson's disease** is a brain disorder that affects movement, often including shaking and stiffness.

Participants will get 4000 to 6000 lux of light (a measure of brightness) for 60 minutes before bed. The study will last for several months up to 8 years. It has been found that this therapy can improve mood, anxiety, and movement in people with PD. This therapy is considered safe and can help with **insomnia** (trouble sleeping) and daytime sleepiness.

• This study involves long-term participation, from several months to 8 years.
• Participants must maintain their usual PD medication regimen.
• People with certain conditions, like vision problems or severe mental illness, cannot join.

If you have been diagnosed with PD and are on stable medication, you might qualify to take part in this study to explore the effects of light therapy.