Tear-derived extracellular vesicles as diagnostic biomarkers for ocular and neurodegenerative diseases: opportunities and challenges

In recent years, the prevalence of ocular diseases has increased considerably. However, timely diagnosis and treatment are hampered by the challenge of early detection since symptoms often appear in advanced stages. Emerging research highlights extracellular vesicles (EVs) as potential biomarkers for ocular diseases, with tear-derived EVs offering a minimally invasive source for early diagnosis. Tears play a crucial role in maintaining eye health and reflect the physiological state of the eye; thus, abnormalities in tear composition can provide valuable insight into inflammatory eye diseases. Studies have demonstrated the utility of tear-derived EVs in identifying biomarkers not only for inflammatory eye diseases but also for neurodegenerative disorders, as they carry molecular signatures (including proteins and various RNA species) reflective of their cells of origin. In this review, we discuss the potential of tear-derived EVs as biomarkers for early detection and monitoring of ocular and neurodegenerative diseases and highlight the importance of standardizing tear collection and EV isolation protocols to ensure reproducibility.