To investigate the effect of frequent use of artificial tears on dry eye syndrome (DES) by analyzing the changes in total protein concentration, lipocalin concentration, and the ratio of lipocalin-to-total protein concentration in tears.

A prospective study was performed on 24 eyes of patients with DES and 24 eyes of control subjects. Artificial eye drops were applied a total of eight times (15-minutes intervals) to all participants. The concentrations of total protein and lipocalin in tears were analyzed before, and after one, two, four, and eight applications. The ratio of lipocalin-to-total protein concentration was also analyzed.

Total tear potein concentration of 3.35 mg/mL had decreased to 3.16 mg/mL after use of artificial tears for control while it had decreased from 1.53 to 0.87 mg/mL for patients. Both groups showed significant decrease ( p = 0.04, p < 0.01, respectively). Lipocalin concentration also showed significant decreases in both control and DES patients for all applications (from 1.15 to 0.85 mg/mL for control, and from 0.49 to 0.22 mg/mL for DES patients, both, p < 0.01). The change in the ratio of lipocalin-to-total protein concentration was significant in the control group ( p = 0.03) but not in the patient group ( p = 0.21).

A significant decrease was observed in the concentrations of total protein and lipocalin in the DES patient group. The ratio of lipocalin-to-total protein concentration was also significantly decreased when eye drops were applied four times. These results suggested that the frequent use of artificial eye drops exacerbated DES.