Non-Invasive Fundus Retinal Detection Technology for Early Diagnosis of Parkinson's Disease

Inclusion Criteria: * 1\. Aged 40-80 years; 2. Parkinson's Disease Group: Patients who meet the 2015 International Movement Disorder Society clinical diagnostic criteria for Parkinson's disease, with a Hoehn and Yahr stage of 1 to 2.5 and a disease duration of ≤5 years; 3. Parkinson's Syndromes Group: Patients who meet the International Movement Disorder Society diagnostic criteria for atypical parkinson's syndromes (including progressive supranuclear palsy, dementia with Lewy bodies, and corticobasal degeneration), multiple system atrophy (P subtype), or secondary parkinson's syndrome (drug-induced: having taken antipsychotic medications for ≥3 months; vascular: confirmed by brain MRI showing leukoaraiosis/lacunar infarction), with a disease duration of ≤5 years; 4. Essential Tremor Group: Patients who meet the 2018 International Movement Disorder Society clinical diagnostic criteria for essential tremor, with no parkinsonian symptoms, and a disease duration of ≥1 year; 5. Healthy Control Group: Individuals with no parkinsonian symptoms (confirmed by neurological examination) and no use of antipsychotic/dopaminergic medications in the past 3 months; 6. All subjects have provided written informed consent and are willing to comply with the study procedures. Exclusion Criteria: * 1\. Presence of severe ocular fundus diseases, such as glaucoma, cataract, retinal detachment, macular degeneration, etc; 2. Inability to tolerate the non-invasive fundus retinal detection; 3. Known allergy or investigator-suspected high risk of allergy to anti-PD drugs; 4. Presence of severe cardiovascular or cerebrovascular diseases (e.g., coronary heart disease, myocardial infarction, stroke, etc.), hepatic or renal dysfunction, cancer, or other conditions that may affect the prognosis; 5. Pregnancy or lactation; 6. Presence of active infectious diseases (e.g., tuberculosis, AIDS) or systemic inflammatory diseases (e.g., rheumatoid arthritis); 7. Presence of psychiatric disorders.