Non-invasive Diagnosis of Parkinson's Disease

Inclusion criteria for Parkinson's group: * Age 60-80 years * Diagnosis of idiopathic Parkinson's disease * Ability to understand spoken and written Swedish * Ability to personally provide consent to participate in the study * At least one healthy eye for retinal photography Inclusion criteria for control group: * Age 60-80 years * Ability to understand spoken and written Swedish * Ability to personally provide consent to participate in the study * At least one healthy eye for retinal photography * Healthy as defined below Exclusion criteria: * At least one eye must not have retinal disease, glaucoma, or vascular eye disease (such as embolism) * Angle-closure glaucoma or other contraindication to mydriatic drops * Low functional ability that makes participation in examinations impossible * Diagnosed dementia * Specifically for the control group: Not healthy according to the definition below Definition of healthy: * No diagnosed or suspected Parkinson's disease * No diagnosed or suspected cognitive disease * No psychiatric disease affecting cognition (e.g., psychotic disorder or major depression) * Cognitive testing with MMSE ≥ 26 points (out of a maximum of 30) and ≥ 8 points on the clock-drawing test