Purpose: To compare tear film osmolarity (TFO) between patients with diabetes mellitus (DM) and normal healthy individuals. Methods: In this prospective case-controlled study, the TFO in 46 normal subjects (control group) and 55 patients with DM (study group) was evaluated. TFO in millios-mole (mOsm) was measured by using an auto-osmometer. The serum levels of glycosylated hemoglobin (HbA(1)c) and blood glucose in all participants were also measured. Mean outcome measures were TFO and its relationship with HbA(1)c level and duration of DM. Results: Mean TFO was 320.40 +/- 21.80 mOsm/l in the study group and 308.22 +/- 18.16 mOsm/l in the control group (p < 0.001). The TFO values were significantly associated with duration of DM (r = 0.476, p < 0.001), but no significant correlation was found with HbA(1)c level (r = 0.225, p = 0.114). Conclusions: The study shows a significantly higher TFO in patients with DM than in the healthy controls. TFO also correlates with the duration of DM. copyright (C) 20135. Karger AG, Basel