This study tests a new way to help people with Parkinson's disease (PD) sleep better. PD is a brain disorder that causes movement problems and other issues, such as trouble sleeping. Many people with PD have insomnia, which means they can't sleep well. The study uses a special light that flickers at 40 times per second (40 Hz) to see if it helps people with PD sleep better. People will be divided into two groups: one group will receive the 40 Hz flicker light and the other will get a regular light. They will use the light for 30 minutes each night for a week. The safety of the light therapy will also be checked.

• The study lasts for 7 days, with nightly 30-minute sessions.
• Participants must have PD and trouble sleeping.
• Safety checks and sleep quality assessments will be conducted.

Participants need to be aged 50-75, have had PD for 10 years or less, and have stable PD medication before joining the study. They should not have other serious health problems or be in another study recently.