Parkinson’s disease is a movement disorder that affects around 10 million people around the world. It is characterized as a chronic and neurodegenerative disorder that leads to tremors, slowness of movement, impaired balance, and other non-motor symptoms such as sexual dysfunction, loss of senses, and gastrointestinal issues. But perhaps one of the most common issues with patients with Parkinson’s disease (PD) is the prevalence of eye and vision issues. Symptoms ranging from mild such as dry eyes, blurry vision, and trouble with depth and perception were found to be more common with people with PD according to a journal article published in Neurology.
Based on the study, patients with Parkinson’s disease often suffer from irregular eyesight, an ophthalmology disorder that’s also related to postural and gait instability. This increases the person with PD’s risk of fall and fall-related injuries. A large percentage of people with Parkinson’s also underreport their eye and vision problems. This is also often overlooked by doctors.
Increased risk of vision impairment is also common among patients with Parkinson because of one of the disease effects in retinal dopamine depletion and decrease of dopaminergic innervation of the visual cortex. Both of these can lead to ocular problems such as color sensitivity and blindness, diminished vision oculomotor control, and visuospatial construction.
The study is part of a bigger study on visual impairments in Parkinson’s’ Disorder. Using a different set of screening questionnaires developed by neurologists and ophthalmologists, the research aims to understand the prevalence of several ophthalmologic symptoms in people with Parkinson’s. It also explores how these ophthalmologic symptoms (e.g color brightness issues, double vision, depth perception problems, and visual hallucinations) affect their daily life functioning.
The questionnaire originally included 22 questions on ophthalmologic symptoms and was revised to 17 to improve readability and logical validity. It also includes a set of demographic questions and is categorized into four domains of ophthalmologic disorders, according to ocular structures: optic nerve, oculomotor, intraocular, and ocular surface. Each domain was given a set of 4 questions.
The questionnaire was distributed by chosen study centers and university hospitals in the Netherlands and Austria between December of 2016 and July 2018. A total of 1,098 people participated in the study and answered the questionnaire. 848 of those are patients with PD while 250 are age-matched controls. After getting their local ethical approval, the study was conducted in accordance with the Declaration of Helsinki. All study participants were volunteers and are anonymous.
● Among patients with PD, 82% have reported 1 or more ophthalmology symptoms compared to 48% of the control group.
● Data also reveal that 68% of people with Parkinson’s reported that eye vision problems have interfered with their daily activities.
● Almost all ophthalmologic symptoms were more common in patients with PD than the control group.
● Patients with PD encountered more difficulties with daily activities due to ophthalmologic symptoms than the control group.
● Patients experienced the greatest interference of ophthalmologic symptoms during the following activities: reading (52%), driving (33%), watching television (28%), and working on the computer (28%).
● Participants with PD fell more frequently than controls (PD: 4% daily or weekly, 28% once or twice a month; controls: 0% daily or weekly, 12% once or twice a month
● 53% of patients with PD reported moderate to severe effects of ophthalmologic symptoms on their quality of life.
● 63% of patients reported a problem in the ocular surface domain. In PD, the most common ocular surface disorder is dry eyes, which can cause decreased vision and contributes to reading difficulties.
● Alterations in the visual network from the retina to higher cortical brain regions have been found in patients with PD and is believed to be the major cause of ophthalmologic symptoms.
● Vision and eye problems in the intraocular and optic nerve domains were twice as frequent among patients with PD than controls. These are caused by the prevalence of cataracts.
● Oculomotor symptoms were also more common among patients with PD. These result in deficits in oculomotor pathways in the brainstem and frontal lobes. It can also cause hypsometric eye movements.
● Cortical involvement can also affect cortical visual areas. This part is important for the initiation of eye movements, target selection, and responses to visual stimuli.
● The study has found a correlation between Parkinson’s disease and neovascular macular degeneration. These conditions are the cause of changes in color and contrast of our vision, poor night vision, and metamorphopsia (a visual defect that causes lines to look curved.)
The sampling method may have led to selection bias because more patients with visual complaints are more likely to respond to the questionnaire. This can cause overestimation of ophthalmologic symptoms.
There is also a potential for self-report bias for the diagnosis of PD. Even when a patient has been diagnosed by a neurologist, there is a 25% percent of misclassification among cases. The researchers minimized the problem by only inviting patients with diagnosis of PD by a neurologist with experience in movement disorders in all 3 centers.
The unverified nature of the questionnaire can also be classified as a limitation. The connection between the ophthalmologic symptoms reported in the study and the actual ophthalmologic diseases has not yet been known. This needs to be further studied.
As we age, vision problems are often common, however, it’s also important to know that there are some vision changes that are due to Parkinson’s Disease. From the study, we can refer that the high prevalence of ophthalmologic symptoms and its negative consequences on the daily life of patients with PD is something that needs to be given solutions in both research and clinical practice.
Patients who report ophthalmologic symptoms should be further assessed. The questionnaire can help patients with PD identify other ophthalmologic symptoms that they might have missed, and enable them to get timely referral and treatment. However, the questionnaire must be further optimized for use in screening.