Visual Dysfunction in Parkinson’s Disease

Abstract

Non-motor symptoms in Parkinson’s disease (PD) include ocular, visuoperceptive, and visuospatial impairments, which can occur as a result of the underlying neurodegenerative process. Ocular impairments can affect various aspects of vision and eye movement. Thus, patients can show dry eyes, blepharospasm, reduced blink rate, saccadic eye movement abnormalities, smooth pursuit deficits, and impaired voluntary and reflexive eye movements. Furthermore, visuoperceptive impairments affect the ability to perceive and recognize visual stimuli accurately, including impaired contrast sensitivity and reduced visual acuity, color discrimination, and object recognition. Visuospatial impairments are also remarkable, including difficulties perceiving and interpreting spatial relationships between objects and difficulties judging distances or navigating through the environment. Moreover, PD patients can present visuospatial attention problems, with difficulties attending to visual stimuli in a spatially organized manner. Moreover, PD patients also show perceptual disturbances affecting their ability to interpret and determine meaning from visual stimuli. And, for instance, visual hallucinations are common in PD patients. Nevertheless, the neurobiological bases of visual-related disorders in PD are complex and not fully understood. This review intends to provide a comprehensive description of visual disturbances in PD, from sensory to perceptual alterations, addressing their neuroanatomical, functional, and neurochemical correlates. Structural changes, particularly in posterior cortical regions, are described, as well as functional alterations, both in cortical and subcortical regions, which are shown in relation to specific neuropsychological results. Similarly, although the involvement of different neurotransmitter systems is controversial, data about neurochemical alterations related to visual impairments are presented, especially dopaminergic, cholinergic, and serotoninergic systems.

Through the eyes of Parkinson\'s: A narrative review of clinical spectrum and ophthalmological challenges in Parkinson’s disease

“…Dopamine significantly impacts several visual functions such as light adaptation, oculomotor function, contrast sensitivity, color perception, visuospatial construction, and spatial working memory. 12 Insufficient dopamine in PD leads to various visual abnormalities, including diplopia. PD patients are also prone to eyelid apraxia, blepharospasm, and dry eyes.…”

Susceptibility to geometrical visual illusions in Parkinson’s disorder

“…VIs have been widely used as a tool to investigate how visual perception develops (e.g., Doherty et al, 2010 ) and the impact of neuropsychological disorders such as schizophrenia (for a review see King et al, 2016 ; Costa et al, 2023 ) and autism (for a review see Gori et al, 2016 ). Although impairment of visual perception (e.g., hallucinations) is now well established in Parkinson’s disorder (PD) ( Sauerbier and Ray Chaudhuri, 2013 ; Weil et al, 2016 ; Nieto-Escamez et al, 2023 ), research has yet to investigate how PD affects susceptibility to VIs. Furthermore, depth perception—which is linked to VI susceptibility (e.g., Gregory, 1963 ; Doherty et al, 2010 ; Gregory, 2015 ) and increased risk of falling ( Cummings et al, 1995 )—is shown to be affected in PD ( Maschke et al, 2006 ).…”

“…Dopamine has also been shown to influence visual perception in PD. Multiple studies have found that retinal dopamine levels and dopaminergic innervation surrounding the fovea are reduced in PD ( Harnois and Di Paolo, 1990 ; Sauerbier and Ray Chaudhuri, 2013 ; Nieto-Escamez et al, 2023 ), resulting in visual perception deficits such as poorer light adaptation and decreased contrast sensitivity (e.g., Pieri et al, 2000 ; Armstrong, 2015 ). Other visual deficits that are linked to dopamine deficiency include greater thresholds for motion detection (e.g., Trick et al, 1994 ), color discrimination (e.g., Büttner et al, 1994 ), as well as visuospatial deficits (e.g., Gibson et al, 1987 ; for an overview of dopamine-related deficits in PD, see Brandies and Yehuda, 2008 ).…”

“…Another hallmark of PD is the pathophysiology of the basal ganglia ( Obeso et al, 2000 ). The basal ganglia are believed to control motor and cognitive functioning ( Macpherson and Hikida, 2019 ); however, recent research has implicated their role in visual perception ( Maschke et al, 2006 ; Nieto-Escamez et al, 2023 ). Maschke et al (2006) showed that PD patients and patients with spinocerebellar ataxia (a movement disorder) made greater errors when estimating the slant of an illusory display (Ames Trapezoidal Window).…”

Unveiling the Hidden Challenges: Non-Motor Disorders in Parkinson’s Disease

“…These symptoms include a range of visual issues, such as dry eyes, blink rate reduction, abnormal eye movements, contrast sensitivity and acuity problems, visuospatial challenges, attention difficulties, and perceptual disturbances, often leading to visual hallucinations. Nieto-Escámez et al's [25] review aims to provide a comprehensive understanding of these visual disruptions, exploring their neuroanatomical, functional, and neurochemical underpinnings, including the structural and functional changes in cortical and subcortical regions and their connections to neuropsychological findings, while also considering the involvement of various neurotransmitter systems like dopamine, acetylcholine, and serotonin.…”