Visualization of the Precorneal Tear Film Using Ultrahigh Resolution Optical Coherence Tomography in Dry Eye

Purpose: To visualize the precorneal tear film (PCTF) in dry eye patients using ultrahigh resolution optical coherence tomography (UHR-OCT). Methods: A custom-built UHR-OCT with ultrahigh resolution (similar to 3 mu m) was used to image the PCTF at the vertical meridian. Eighteen right eyes of 18 previously diagnosed dry eye patients (9 men and 9 women, age, 47.8 +/- 20.7 years) with aqueous tear deficiency were studied. Images were taken during normal and delayed blinking. The visualized PCTF was measured directly. An indirect calculation was used to obtain the thickness in cases where the PCTF could not be visualized. Results: During normal blinking, the PCTF was visualized in 5 of 18 eyes (27.8%) with an average PCTF thickness of 5.8 mu m (SD, 1.3 mu m). During delayed blinking, the PCTF was visualized in 11 eyes (61.1%) with a significantly increased average thickness of 7.3 mu m (SD, 0.9 mu m; P<0.05). The percent increase of the visualized PCTF thickness was higher during delayed blinking compared with normal blinking (chi(2) test, P<0.05). The averaged PCTF was 4.4 mu m during normal blinking, and the PCTF thickness was significantly increased to 6.6 mu m (SD, 2.9 mu m; P<0.05) during delayed blinking. Conclusions: We report the first visualization of PCTF in vivo in dry eye patients with UHR-OCT. Precorneal tear film can be directly visualized in some eyes during both normal and delayed blinking, and it seemed thicker during delayed blinking compared with normal blinking.