Two components of the tear film could help discriminate healthy patients from those with Parkinson's disease (PD), according to a recent study presented this week at ARVO in Honolulu, Hawaii. Researchers tested tears from 60 PD patients for alpha-synuclein, matrix metallopeptidase 9 (MMP-9), lactoferrin (LF), oligomeric alpha-synuclein and total protein concentration and compared the results with tears from 30 healthy controls.

While MMP-9 and LFI did not vary much between the two groups, other protein concentrations were more telling. In the PD patients, total alpha-synuclein measurements were significantly lower than in healthy controls. At the same time, oligomeric alpha-synuclein levels were significantly higher in the PD patients than in the healthy controls and, overall, the total protein concentration in the PD patients was significantly higher.

These results led the researchers to believe that alpha-synuclein and oligomeric alpha-synuclein could potentially serve as biomarkers for PD. “Detection of such changes may have utility in early diagnosis of Parkinson's disease, before the emergence of motor symptoms which are often delayed years beyond the onset of non-motor symptoms of the disease, thus enabling earlier interventions,” the study concluded.

Clinical application of this knowledge may be a ways off, however. “Currently, the problem is we don’t have the ability to measure these proteins,” says Joseph P. Shovlin, OD, of Scranton, PA. An in-office test would have to be developed. Indications for use will be another hurdle to clear. “If this became a part of clinical practice, I think you’d have to use it in concert with other risk factors such as family history or symptoms.”

Hamm-Alvarez SF, Lew M, Feigenbaum D, et al. Tear proteins as possible biomarkers for Parkinson’s disease. ARVO 2018. Abstract 4909.