Tears Offer Noninvasive Alternative for Diagnosing Neurodegenerative Diseases

Ocular fluids like aqueous humor and vitreous humor contain valuable molecular information about eye health but are difficult to access safely. A wide range of eye diseases are being investigated, but the methods for obtaining aqueous humor and vitreous humor, the fluids inside the eye, are highly invasive, which limits their applicability in routine clinical practice.

Now, researchers have reviewed the growing evidence that tears—specifically their extracellular vesicles (EVs)—could provide a simpler, noninvasive source of biomarkers. Researchers at the Germans Trias i Pujol Research Institute (Badalona, Barcelona, Spain) have summarized the findings of their review of more than one hundred studies exploring this emerging field in the journal Extracellular Vesicles and Circulating Nucleic Acids.

The research team examined the potential of tear-derived EVs —tiny particles secreted by cells that carry proteins, nucleic acids, and lipids—as minimally invasive biomarkers. These EVs can preserve molecular information and may reflect both local ocular and systemic disease processes. The review highlights several key advantages of using tear-derived EVs.

Collecting tears is simple and painless, making it ideal for regular monitoring. Moreover, because EVs can cross both the blood-brain and blood-retinal barriers, they may also provide insight into neurodegenerative conditions beyond the eye, such as Alzheimer’s or Parkinson’s disease. This dual potential positions tear-derived EVs as powerful tools for early detection and disease tracking.

However, the researchers caution that technical hurdles remain before the approach can be integrated into clinical use. A major challenge is the lack of standardized methods for sample collection, storage, and analysis. The authors recommend adopting international pre-analytical codes and adhering to the guidelines set by the International Society for Extracellular Vesicles (ISEV) to ensure consistency and reproducibility across studies.

“I see a field with great potential, but one that is still developing,” said researcher Marta San Roque. “Research on EVs as biomarkers is booming, but when it comes specifically to tear-derived EVs, there are still few studies. This review represents an important first step towards further progress in the field of biomarkers, particularly for the early detection and improved treatment of ocular and neurodegenerative diseases.”

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Germans Trias i Pujol Research Institute