Brain Advance Access published online on March 31, 2009
Brain, doi:10.1093/brain/awp068
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Review Article |
The retina in Parkinson's disease
1 Clinical Ageing Research Unit, Newcastle University, UK 2 Royal Victoria Infirmary, Newcastle upon Tyne, UK 3 Institute for Ageing and Health, Newcastle University, Campus for Ageing and Vitality Newcastle upon Tyne, UK 4 Clinical Ageing Research Unit, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, UK
Correspondence to:
Dr. Neil Archibald, Clinical Research Fellow, Clinical Ageing Research Unit, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, NE4 5PL, UK. E-mail: neil.archibald{at}ncl.ac.uk
As a more complete picture of the clinical phenotype of Parkinson's disease emerges, non-motor symptoms have become increasingly studied. Prominent among these non-motor phenomena are mood disturbance, cognitive decline and dementia, sleep disorders, hyposmia and autonomic failure. In addition, visual symptoms are common, ranging from complaints of dry eyes and reading difficulties, through to perceptual disturbances (feelings of presence and passage) and complex visual hallucinations. Such visual symptoms are a considerable cause of morbidity in Parkinson's disease and, with respect to visual hallucinations, are an important predictor of cognitive decline as well as institutional care and mortality. Evidence exists of visual dysfunction at several levels of the visual pathway in Parkinson's disease. This includes psychophysical, electrophysiological and morphological evidence of disruption of retinal structure and function, in addition to disorders of ‘higher’ (cortical) visual processing. In this review, we will draw together work from animal and human studies in an attempt to provide an insight into how Parkinson's disease affects the retina and how these changes might contribute to the visual symptoms experienced by patients.
Key Words: Parkinson's disease; visual hallucinations; visual perception; retina; dopamine
Abbreviations: DA, dopaminergic; ERG, electroretinogram; L-DOPA, levodopa; LGN, lateral geniculate nucleus; M-cells, magnocellular retinal ganglion cells; MMSE, mini-mental state examination; MPTP, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine; P-cells, parvocellular retinal ganglion cells; PERG, pattern ERG; RNFL, retinal nerve fibre layer; UFOV, useful field of vision; V1, primary visual cortex; VEP, visual evoked potential
Received September 8, 2008. Revised February 26, 2009. Accepted February 27, 2009.