Tear osmolarity testing measures the concentration of dissolved particles in the tear film, providing an objective marker of dry eye disease severity. Elevated osmolarity reflects tear film instability and hypertonicity.
Technique
A small sample of tears is collected, usually from the lower tear meniscus, using a microchip or capillary system. The analyser calculates osmolarity in milliosmoles per litre.
- Requires only a tiny tear volume and is relatively quick
- Values can vary between eyes and over time, so patterns are important
- Higher readings are associated with more severe dry eye
- Care is taken to minimise reflex tearing during sampling
Clinical Role
Tear osmolarity helps confirm dry eye diagnosis, stratify severity, and monitor treatment response. It is one component of a comprehensive dry eye workup.
- Combined with symptom scores and surface staining for full assessment
- Serial measurements can show improvement or deterioration
- Interpretation must account for natural variability and environmental factors
- Useful in clinical practice and research trials as a quantifiable endpoint
