Tear osmolarity and tear film parameters in patients with unilateral pterygium

Purpose: The aim of this study was to evaluate the differences in tear osmolarity and tear film parameters between pterygium-affected and healthy fellow eyes. Methods: The study enrolled 65 patients with unilateral pterygium. Tear osmolarity, tear film break-up time (TBUT), Schirmer I test measurements, fluorescein corneal staining, and conjunctival redness were evaluated. The results were compared between pterygium-affected eyes and healthy fellow eyes of the same patient (controls). The pterygium thickness was measured using optical coherence tomography. We also evaluated the relationship between pterygium thickness and tear osmolarity and between TBUT and Schirmer I test results in eyes with pterygium. Results: The mean tear osmolarity was 307 mOsm/L in pterygium-affected eyes and 294 mOsm/L in control eyes. The mean values of TBUT, Schirmer I test, corneal staining, and conjunctival redness scores were 10.3 +/- 3.4 seconds, 14.8 +/- 9.2 mm, 1.2 +/- 1.1, and 0.9 +/- 0.9 in the pterygium group, whereas the mean values were 12.3 +/- 4.4 seconds, 16.2 +/- 7.2 mm, 0.4 +/- 0.8, and 0.4 +/- 0.7 in the control group, respectively. Eyes with pterygium had significantly higher tear osmolarity levels, corneal staining, and conjunctival redness scores; and lower tear film TBUT and Schirmer I test values than eyes without pterygium (Wilcoxon signed rank test, P < 0.05). There was no significant correlation between pterygium thickness versus tear osmolarity, TBUT, and Schirmer I test values in eyes with pterygium (r = 0.159, 0.738, 0.321, respectively; P > 0.05). Conclusions: This study showed that pterygium is associated with tear hyperosmolarity and abnormal tear film function.