Tears - more to them than meets the eye: why tears are a good source of biomarkers in Parkinson's disease

Biomark Med. 2020 Feb;14(2):151-163. doi: 10.2217/bmm-2019-0364. Epub 2020 Feb 17.


Tears are a known source of biomarkers for both ocular and systemic diseases with particular advantages; specifically, the noninvasiveness of sample collection and a unique and increasingly better-defined protein composition. Here, we discuss our rationale for use of tears for discovery of biomarkers for Parkinson's disease (PD). These reasons include literature supporting changes in tear flow and composition in PD, and the interconnections between the ocular surface system and neurons affected in PD. We highlight recent data on the identification of tear biomarkers including oligomeric α-synuclein, associated with neuronal degeneration in PD, in tears of PD patients and discuss possible sources for its release into tears. Challenges and next steps for advancing such biomarkers to clinical usage are highlighted.

Keywords: Parkinson's disease; biofluid; lacrimal functional unit; lacrimal gland; ocular surface; oligomeric α-synuclein; tearome; tears; α-synuclein.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biomarkers / metabolism*
  • Humans
  • Lacrimal Apparatus / metabolism
  • Neurons / metabolism
  • Parkinson Disease / diagnosis
  • Parkinson Disease / metabolism*
  • Protein Multimerization
  • Protein Transport
  • Sensitivity and Specificity
  • Tears / metabolism*
  • alpha-Synuclein / chemistry
  • alpha-Synuclein / metabolism*


  • Biomarkers
  • alpha-Synuclein