Tear hyperosmosis is considered to be one of the core mechanisms of dry eye.The measurement of tear osmolarity is important in the clinical diagnosis of dry eye.However, relevant study is lack in Chinese population.

The aim was to investigate the relation of tear osmolarity and pathogenesis of dry eye and evaluate the diagnosis value of tear hyperosmosis in dry eye.

Sixty-one consecutive dry eye patients were enrolled in Affiliated Eye Hospital of Wenzhou Medical University from May to August in 2011, including 30 mild and moderate dry eyes and 31 severe dry eyes, and 30 normal volunteers with matched age and gender were collected simultaneously under the informed consent.The visual acuity, Ocular Surface Disease Index (OSDI) questionnaire, osmotic pressure of tear, tear film breakup time (TFBUT), corneal fluorescein staining, conjunctival lissamine green staining, ShirmerⅠtest (SⅠt) without anesthesia and meibomian function were examined in turn in the subjects, and lateral eyes with higher tear osmotic pressure were analyzed.The differences in above indexes among the different groups were statistically compared, and the correlations between the osmotic pressure of tear and clinical parameters were assessed.

The osmotic pressure of tear was (326.46±22.66) mOsm/L in the dry eye group, which was significantly higher than (296.60±10.81) mOsm/L in the normal control group (P<0.05), and the OSDI scores, TFBUT, corneal fluorescine scores, conjunctival staining scores and SⅠt values in the dry eye group were remarkably elevated in comparison with the normal control group (all at P<0.05). The osmotic pressure of tear was (341.90±21.15) mOsm/L in the severe dry eye group, which was significantly higher than (310.50±8.99) mOsm/L in the mild and moderate group (P<0.017). The area under the curve for tear osmolarity in the dry eye group was 0.916, and cutoff value of sensitivity and specificity in dry eye diagnosis was 308 mOsm/L, with the sensitivity value 0.79 and specificity 1.00.The significant correlations were found between the osmotic pressure of tear and OSDI scores, corneal fluorescine scores, conjunctival staining scores and SⅠt outcomes (r=0.338, 0.407, 0.246, -0.461, all at P<0.05). However, the osmotic pressure of tear was not correlated with TFBUT (r=-0.113, P>0.05).

Tears osmotic pressure might be a useful indicator for the diagnosis of dry eye and assessment of severity.A combined application of tear osmolarity measurement with other relevant indexes can improve the diagnostic value.

Dry eye/diagnosis; Tears; Osmolar concentration; Diagnostic techniques, ophthalmological/instrumentation