Light Therapy in Parkinson's Disease

Inclusion Criteria: * According to the criteria of PD diagnosis of the MDS, PD patients were selected as the research object. The clinical symptoms of PD patients were consistent with Hoehn and Yahr stages 2-3. * All PD patients have maintained stable drug treatment for at least one month, signed clinical informed consent and agreed not to adjust drugs throughout the light test and follow-up period. Exclusion Criteria: * Using hypnotic or stimulating drugs. * Using antidepressants, except stable drugs maintained for more than three months; * Visual impairment, such as cataract, glaucoma, blindness, etc; * Cognitive impairment (MMSE \< 24); * There are uncontrollable hallucinations and mental diseases; * There are sleep phase delay / advance syndrome, shift work, jet lag, etc