Visual Dysfunction: An Underrecognized Symptom of Parkinson's?

October 25, 2019

Visual symptoms are a potentially underrecognized and undertreated cause of reduced quality of life in Parkinson disease patients, a new study suggests.

By analyzing data from a large population health survey, researchers from the University of Pennsylvania, Philadelphia, found that visual dysfunction is significantly more common in individuals with Parkinson disease than in the general adult population.

"The idea that visual symptoms may be associated with Parkinson's disease is not new, but this is the first time it has been reported on a population level," lead author Ali Hamedani, MD, told Medscape Medical News.

"In a survey of more than 150,000 individuals, we found that people with a diagnosis of Parkinson's disease were more than twice as likely to report impairment in eyesight than those without a Parkinson's diagnosis, and there were similar increases in long distance or near vision," he noted.

"I think our data confirm what people have already suspected ― that Parkinson's disease is associated with visual impairment ― but this is the largest study ever done to look at this association," he added.

The study was published online October 19 in the European Journal of Neurology.

Problems with vision in Parkinson's disease patients are increasingly being recognized by the patients themselves, their caregivers, and by physicians on a local level, but the problem hasn't been studied comprehensively or documented in large-scale studies before, Hamedani explained.

"We wanted to look in a large cohort of people how visual dysfunction related to Parkinson's disease," he said.

To do this, he and colleague Allison Willis, MD, analyzed data from adults aged 50 years or older from the Survey of Health, Ageing and Retirement in Europe (SHARE), a multinational population-based health survey of adults living in one of 27 European countries and Israel. The survey asked questions about a spectrum of health issues, including medical conditions that had been diagnosed, visual problems, as well as demographic information and other factors.

The diagnosis of Parkinson disease was self-reported. Impairment in overall, distance, or near eyesight was defined as a score of 4 or 5 on a 1–5 scale.

Adjusted logistic regression was used to determine the association between Parkinson disease and self-reported vision.

Results showed that among the 115,240 age-eligible participants in the SHARE study (mean age, 64.3 years), 1438 (1.25%) reported a diagnosis of Parkinson disease.

In adjusted logistic regression models, Parkinson disease was associated with increased odds of impaired overall eyesight (odds ratio [OR], 2.67), distance vision (OR, 2.55), and near vision (OR, 2.07).

Individuals with Parkinson disease were also less likely to report having had an eye examination within the previous 2 years (OR, 0.59), but this did not remain statistically significant after adjusting for confounders.

"This result will provide greater awareness that visual symptoms can be an issue in Parkinson's disease," Hamedani said.

He noted that they did not have information on the duration of Parkinson's in this study, so it was not possible to determine whether vision dysfunction is an early symptom or a later symptom of the condition.

"Ultimately, there may be guidelines for people with Parkinson's disease specific for screening and treatment of visual symptoms, but there is a lot more work to be done before we get there," Hamedani suggested.

"At present, I think we can say that visual dysfunction is something to look out for in Parkinson's disease patients, but the exact nature and significance of these symptoms are not yet clear. And we don't know whether the mechanism is a result of Parkinson's-associated changes in the brain or in the eye."

He noted that there have been some suggestions of a subtle change in color vision in the years before Parkinson's is diagnosed, but patients themselves are unlikely to notice this. "It would have to be uncovered by screening, but it is too early for any recommendations on this," Hamedani said.

"I would say that at present, our results would prompt clinicians to pay more attention to the eyes in Parkinson's patients. They should ask patients if they are having any visual problems and encourage patients to get regular eye examinations. Preventative eye examinations are important for all older adults, especially for patients with Parkinson's disease and similar conditions.

"Eye problems in Parkinson's patients can be numerous and can include dry eyes, double vision, difficulty reading. But the current study didn't address exactly what the issues were."

He added that dry eyes are common in Parkinson's patients because the spontaneous blink reaction is reduced in persons with the condition. Double vision is caused by misalignment of the eyes, and this could be due to problems in areas of the brain involved in coordinating eye movement.

The researchers are planning further work to investigate the specific visual symptoms associated with Parkinson's and how vision affects outcomes such as falls, hallucinations, and cognition.

"I think we need to be thinking outside the box on these outcomes, which may well be reduced by addressing vision issues," Hamedani said.

"Given the important role that vision plays in overall quality of life and the association between vision loss and falls, hip fracture, depression, anxiety, and dementia, visual dysfunction in Parkinson's disease is a significant public health finding regardless of its cause," the researchers add.

Hamedani and Willis receive research support from the National Institutes of Health.

Eur J Neurol. Published online October 19, 2019. Abstract

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