Inclusion Criteria:  Idiopathic Parkinson's disease Hoehn and Yahr stage between I and IV Mini-Mental State Examination score above 24.  Exclusion Criteria:  Major psychiatric or other neurological conditions, Rheumatological diseases Ophthalmic diseases Orthopedic diseases Ongoing or previous treatment with neuroleptic drugs Patients with deep brain stimulation Any change in dose or regimen of the anti-parkinsonian therapy in the last month before enrolment.