Affiliations: Department of Neurology, Seoul National University-Seoul Metropolitan Government Boramae Medical Center, Seoul, Republic of Korea | Department of Ophthalmology, Seoul National University-Seoul Metropolitan Government Boramae Medical Center, Seoul, Republic of Korea | Department of Neurology and Movement Disorders Center, Seoul National University Hospital, Seoul, Republic of Korea | College of Medicine, Seoul National University, Seoul, Republic of Korea
Note:  Correspondence to: Jee-Young Lee, M.D., Ph.D., Department of Neurology, SNU-SMG Boramae Medical Center and College of Medicine, Seoul National University. Dongjak-gu, Shindaebang-dong, Boramae 5 Road 20, 156-707 Seoul, Republic of Korea. Tel.: +82 2 870 2476; Fax: +82 2 831 2826; Email: email@example.com
Abstract: Visual symptoms are a common feature in patients with Parkinson's disease (PD), and retinal dopamine loss and dysfunctions in foveal vision have been described in PD patients. Because visual hallucination (VH) is a specific feature of PD which is differentiated from other parkinsonian disorders, defective visual information processing from both the central and peripheral pathways is suggested to be the pathophysiological mechanisms of VH in PD. Decreased visual acuity as well as impaired contrast sensitivity and color vision is known to be related to the appearance of VH in PD. However, these functional studies were also affected by cognitive or cortical dysfunctions; thus, structural imaging can more reliably reflect visual afferent dysfunction. Recently, optical coherence tomography (OCT) scans have been used to investigate the structural changes in the retina in vivo. Segmental measures of the vertical retinal layers by OCT provide structural evidence for retinal dopamine loss and foveal dysfunction in PD. Retinal nerve fiber layer (RNFL) thinning in PD was shown to be significantly associated with VH and correlated with PD duration and severity. Thus, there is a possibility that the retina could be a biomarker for disease progression and risk of VH in PD. A standard protocol for OCT studies in PD with more accurate measures of the retinal layers needs to be developed in the future.