Reflex tears may provide biomarker for Parkinson’s disease

VANCOUVER, British Columbia — Researchers saw changes in oligomeric alpha-synuclein in both basal and reflex tears in patients with Parkinson’s disease, according to a study presented here at the Association for Research in Vision and Ophthalmology meeting.

“Changes are more pronounced and have a stronger increase ... when we measure in reflex tears,” principal investigator Sarah F. Hamm-Alvarez, PhD, told Healio.com/OSN.

“The diagnosis of Parkinson’s disease is challenging before patients develop motor symptoms such as tremor or other movement abnormalities,” she said. “By this time, significant neurological damage has occurred. Usually this is irreversible.

“There’s a lot of interest in identifying it before this damage has occurred so, hopefully, therapeutics can be developed to intervene and prevent it,” she added.

Hamm-Alvarez said her group has been working in the area of tear biomarkers for Sjögren’s syndrome, “and we started thinking about the fact that many of the symptoms that Parkinson’s patients have are related to symptoms of cholinergic dysfunction.

“Parkinson’s patients have low gastric motility, which is a symptom of a cholinergic nerve dysfunction,” she continued, “and also we’re aware that the lacrimal gland is highly innervated by cholinergic nerves and also by dopaminergic nerves. So we thought we’d look to see if the tear film is affected in Parkinson’s disease patients.”

The researchers evaluated basal tears in 93 patients with Parkinson’s disease and 82 controls and reflex tears in 84 patients with Parkinson’s and 84 controls, Hamm-Alvarez said.

Basal tears were collected by using Schirmer’s test with a local anesthetic, and reflex tears were collected using Schirmer’s test without anesthetic.

Samples were analyzed for total alpha-synuclein, oligomeric alpha-synuclein, lactoferrin and matrix metallopeptidase.

“We have determined that there is a strong correlation of oligomeric synuclein in tears of patients with Parkinson’s,” Hamm-Alvarez said. “Our patients are homogeneous. They’ve had Parkinson’s disease for at least 6 years. Now we’d like to know whether the levels of biomarker change over time with active disease.

“We’re tremendously excited by the potential that we might have a simple and noninvasive test that we may be able to apply and eventually could detect Parkinson’s disease in undiagnosed patients at an earlier stage,” she said. “That would be our goal.”– by Nancy Hemphill, ELS, FAAO

Reference:

Edman MC, et al. Tear biomarkers for Parkinson’s disease in basal versus reflex tears. Presented at: Association for Research in Vision and Ophthalmology; April 28-May 2, 2019; Vancouver, British Columbia.

Disclosures Hamm-Alvarez reports no relevant financial disclosures. Please see the study abstract for all other authors’ relevant financial disclosures.