Reduced Visual Contrast Acuity Common In Parkinson's Patients

New findings published in the Journal of Parkinson's Disease show that patients with Parkinson's disease have difficulties with visual acuity in low-contrast images.

"Visual impairments can have a significant impact on quality of life and day-to-day functions," lead study author Charles H. Adler, MD, PhD, Department of Neurology, Mayo Clinic College of Medicine, Scottsdale, Ariz, said in a news release. "However, impaired contrast sensitivity in PD patients is a topic that has received relatively little attention in clinical practice. The electronic form of low contrast acuity letter chart we used in this study combines contrast sensitivity with visual acuity testing and is quick and easy to administer. It is portable, quantitative, and adjustable for testing distances and contrast levels."

The degree of low-contrast visual deficiency along with PD severity suggests that visual testing could potentially help provide a window into the diagnosis and treatment of the cognitive health issue.

The study was composed of 32 patients with PD and 71 control subjects. All received a neurological examination that included the Unified Parkinson's Disease Rating Scale (UPDRS), and vision testing using the Variable Contrast Acuity Chart displayed on an Apple® iPad 2. Usual corrective lenses were worn by subjects that required them.

The testing was based on high contrast with distances at 40 cm and 2 m. The chart design and testing protocol were based on the Bailey-Lovie and Early Treatment of Diabetic Retinopathy Study (EDTRS) visual acuity tests that are the standards in ophthalmology clinical trials. With a scale of visual acuity based on the number of letters correctly identified, PD patients could see just about 10 percent fewer letters than those in control groups in the low-contrast tests at either distance and in the high-contrast tests at 2 m. Futhermore, there was no statistically significant difference between PD and control subjects in the high-contrast testing at 40 cm.

"Visual impairments can have a significant impact on quality of life and day-to-day functions," concluded Adler. "However, impaired contrast sensitivity in PD patients is a topic that has received relatively little attention in clinical practice. The electronic form of low contrast acuity letter chart we used in this study combines contrast sensitivity with visual acuity testing and is quick and easy to administer. It is portable, quantitative, and adjustable for testing distances and contrast levels."