If You Notice This With Your Vision, Get Checked for Parkinson's

This vision test may help put a diagnosis within reach.

Many patients with Parkinson's disease (PD) experience motor symptoms—the most common among them being tremor. And while this symptom often helps inform a diagnosis, experts say that it can be easily confused with another condition which shares several of the same characteristics as PD, known as essential tremor (ET). However, one recent study has found that there is another far less common symptom that may help distinguish PD from similarly presenting ailments. Surprisingly, you may notice it in the form of a change in your vision. Read on to find out which visual symptom to look out for, and when you might be most likely to experience it.

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If you have poor color discrimination, get checked for Parkinson's disease.

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According to a 2012 study published in the journal Movement Disorders, color discrimination deficit—or a reduced ability to distinguish between similar colors—is a common non-motor symptom of Parkinson's disease.

With the aim of identifying connections between physical alterations in the brains of PD patients and those with poor color discrimination, the research team gathered 66 PD patients without dementia and 20 healthy non-PD patients to take the Farnsworth-Munsell 100 hue test (FMT), a measure of color vision acuity. In addition to the vision test, subjects then underwent a neuropsychological assessment for mild cognitive impairment associated with Parkinson's.

The researchers found that cognitive impairment from PD significantly affected their subjects' performance on the hue test, and was also linked with white-matter alterations in the right posterior region of the brain.

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The hue test may help distinguish between PD and similar disorders.

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A separate 2011 study on the subject took a closer look at differences in color discrimination in those with PD versus those with essential tremor (ET), which shares many similar symptoms. "In some cases, it is difficult to differentiate essential tremor from Parkinson's," says the study, published in the European Journal of Neurology. "In addition, there is considerable controversy regarding the relationship between PD and ET. The objective of this study was to compare color discrimination dysfunction amongst patients with PD and ET and to investigate the clinical relevance," the researchers wrote.

By comparing 54 patients with PD, 36 patients with ET, and 34 age-matched controls, the team found "there were significant differences in the total error scores (TES) of the FMT [hue test] amongst the three groups." Those with Parkinson's had the highest error rate of the groups, suggesting that "color vision abnormalities may be one of the non-motor clinical characteristics of PD-related dysfunction in contrast to ET."

The rate of error rose with severity of symptoms.

A senior man sitting on the couch and holding a cane

The researchers noted the Parkinson's patients who demonstrated high error rates in their vision tests were more likely to have more severe or advanced symptoms of PD. "The motor symptom severity in PD correlated with the FMT abnormalities, especially with regard to the axial symptoms," the team wrote. Axial symptoms include freezing of gait, postural instability, changes in trunk posture, and dysarthrophonia—the voice and speech chances related to PD.

Conversely, those with poor color discrimination may also find that it complicates their existing motor symptoms by altering depth perception. "Related to loss of color discrimination is change in depth perception, or the ability to estimate the relative distance and relief of objects. Lack of color contrast results in a flat visual effect, or decreased depth perception and inability to judge distances," says a 2012 study published in the journal Geriatric Physical Therapy. "As a result of the inability to judge distances, older persons may have difficulty estimating the height of curbs and steps and may have difficulty with activities of daily living that require distance judgment, including feeding tasks," that team concluded.

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There may be several other causes for your poor color contrast.

black woman doctor administering eye test to young patient

If you do experience poor color contrast, there may be reasons other than Parkinson's for your change in vision. According to the Mayo Clinic, there are several diseases that cause color deficits, including sickle cell anemia, diabetes, macular degeneration, Alzheimer's disease, multiple sclerosis, glaucoma, chronic alcoholism, and leukemia. Additionally, you may notice color distinction abnormalities as a result of certain medications, exposure to certain chemicals, inherited visual disorders, or aging.

Speak with your doctor if you notice any changes in your own vision.

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Lauren Gray
Lauren Gray is a New York-based writer, editor, and consultant. Read more
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