Changes of Retina Are Not Involved in the Genesis of Visual Hallucinations in Parkinson's Disease

Parkinson's disease (PD) is characterized by motor and nonmotor symptoms. Nonmotor symptoms include primarily visual hallucinations (VH). The aim of our study was to establish whether patients with PD and visual hallucinations (PDH+) have structural changes of retina detected by an optical coherence tomography (OCT) in comparison with PD patients without visual hallucinations (PDH-). We examined 52 PD patients (18 with VH, 34 without VH) and 15 age and sex matched healthy controls. Retinal nerve fiber layer (RNFL) thickness and macular thickness and volume were assessed by OCT. Functional impairment of retina was assessed using 2.5% contrast sensitivity test. For OCT outcomes we analyzed 15 PDH+ and 15 PDH- subjects matched for age, gender, and PD duration. For contrast sensitivity we analyzed 8 pairs of patients matched for age, gender, and visual acuity. There was no significant difference in RNFL thickness and macular thickness and macular volume between 15 PDH+ and 15 PDH- subjects, and also between a group of 44 PD patients (both PDH+ and PDH-) and 15 age and gender matched healthy controls. No significant difference was found for 2.5% contrast sensitivity test values between PDH+ and PDH- subjects. Therefore we conclude that functional and structural changes in retina play no role in genesis of VH in PD.