A Look At Vision Issues in PARKINSON’S DISEASE
A lesion in the visual cortex renders some people technically blind. While their actual eyes are still functional and can perceive the source of light or even discern and emotional expression on someone’s face, they are still considered legally blind. A person with PARKINSON’S DISEASE, may have intact eye function and no lesion in the visual cortex, but may be unable to perceive the emotion on another’s face or grasp an object that is moving.
Dr. Nico Diederich has been studying vision deficits in PARKINSON’S DISEASE for many years. He is a Clinical Senior Researcher at the University of Luxembourg Centre for Systems Biomedicine and is presently a visiting scholar at Rush University Medical Center in Chicago, IL. Together with three more researchers from Rush, they recently published a research study entitled “Are patients with Parkinson’s disease blind to blindsight?” in the scientific journal Brain that explains their concept for understanding visual impairment in PARKINSON’S DISEASE.
Dr. Diederich describes blindsight as the ability of the technically blind to accurately perceive a source of light or detect a rapid motion or even an emotional expression on someone’s face…without being consciously aware of “seeing”. He describes it as similar to a reflex. In “blindsight”, visual stimuli can pass through lower areas of the brain and still be processed to turn in a response. His research on PARKINSON’S DISEASE has found that although PARKINSON’S patients have no problems with their general vision, their responses are impaired; hence he calls them “blind to blindsight”.
Approximately a third of people with PARKINSON’S also experience hallucinations, when small, involuntary movements flutter in the corner of the eye may be mistaken for people or animals. Taken together, these visual impairments with a mistaken perception or a slow response time can greatly hinder the patient’s ability to drive and definitely negatively affect their quality of life.
“We have analyzed all known visual impairments in PARKINSON’S patients and compared them with the “blindsight” syndrome. We could show that mostly evolutionary old brain networks are impaired and underlie the visual impairments observed in PARKINSON’S DISEASE, states Dr. Diederich.
Glenn Stebbins, Ph.D. and Christopher G. Goetz, M>D> from Rush University Medical Center in Chicago and Christine Schiltz, PHD, from the University of Lusembourg contributed to this research.
Original publication: Nico J Diederich, Glenn Stebbins, Christine Schiltz, Christopher Goetz (2014) Are patients with Parkinson’s disease blind to blindsight?Brain; doi: 10.1093/brain/awu/094
Review by Marcia McCall