To evaluate tear osmolarity with the recently introduced TearLab system (TearLab Corporation, San Diego, CA) in patients with non-Sjögren syndrome dry eye (NSSDE) and Sjögren syndrome dry eye (SSDE), and in healthy subjects, and to compare the results with those from classical dry eye tests.
Thirty-nine eyes of 21 patients with NSSDE, 39 eyes of 20 patients with SSDE, and 44 eyes of 22 healthy individuals were included in the study. Tear osmolarity was measured with the TearLab system, lid-parallel conjunctival folds score was examined with the slit lamp, and then the classical diagnostic tests such as Schirmer I test, tear film break-up time, and corneal staining were carried out, followed by the examination of meibomian glands and corneal transparency.
Mean tear osmolarity was 296.77 ± 16.48 mOsm/L in NSSDE (15% abnormal), 303.36 ± 17.22 mOsm/L in SSDE (23% abnormal), and 303.52 ± 12.92 mOsm/L in the control group (16% abnormal; P = 0.018, Kruskal-Wallis). Schirmer test, corneal staining, tear film break-up time, and meibomian gland status were significantly different in the 2 patient groups when compared with those in the control group (P < 0.0001). In the control and SSDE groups, no significant correlation was disclosed between tear osmolarity and any of the dry eye tests performed.
Tear hyperosmolarity is considered a key factor that leads to dry eye symptoms and to the progression of clinical signs. Osmolarity measurements with the TearLab system disclosed no ability to distinguish between healthy individuals and patients with dry eye. This suggests that the TearLab device should not be used alone but in combination with classical dry eye tests.