Tear Biomarkers in Veterinary Species: An Updated Review with Special Focus on Dogs and Cats.

Tear fluid offers a non-invasive, diagnostically promising biomarker source for detecting ocular and systemic diseases in dogs and cats.

This narrative review provides a comprehensive update on tear fluid as a source of biomarkers in veterinary species, with particular emphasis on dogs and cats. The tear film is described as a multilayered structure—comprising lipid, aqueous, and mucin layers—that not only maintains ocular surface homeostasis but also reflects systemic physiological and pathological states. The review details the biochemical composition of tear fluid, including proteins, lipids, electrolytes, and other molecules, and examines how these components change under various disease conditions, both ocular and systemic. Sampling methodologies are critically evaluated, including Schirmer tear test strips, capillary tubes, and absorbent materials, with discussion of their respective advantages, limitations, and potential impact on sample integrity and biomarker detection. The authors highlight the growing body of evidence supporting tear-based diagnostics as a non-invasive alternative to blood or tissue sampling in veterinary patients. Identified tear biomarkers show promise for early disease detection, monitoring of disease progression, and therapeutic response assessment. The review positions tear fluid collection as a clinically feasible, minimally stressful procedure suitable for routine veterinary practice. Overall, this work underscores the translational potential of tear biomarker research from human to veterinary medicine and advocates for further standardization of collection and analytical techniques to advance this diagnostic modality in clinical and research settings.

This summary was distilled by AI and may occasionally misinterpret data. Confirm critical details with the primary literature before clinical application.