Measurement of Tear Film Thickness Using Ultrahigh-Resolution Optical Coherence Tomography

Abstract

PURPOSE: To visualize the precorneal tear film with ultrahigh-resolution spectral domain optical coherence tomography, enabling quantification of tear film thickness in healthy subjects. METHODS: A custom-built spectral domain optical coherence tomography system comprising a broadband titanium:sapphire laser operating at 800 nm and a high-speed charge coupled device (CCD) camera with a read-out rate of 47 kHz was used for measurement of precorneal tear film thickness. The system provides a theoretical axial resolution of 1.2 μm in tissue. The signal-to-noise ratio close to the zero delay was measured with 94 dB. A total of 26 healthy subjects were included in this study. Measurement was started immediately after blinking and averaged over a period of 1 second. In a subset of eight healthy subjects, the reproducibility of the approach was studied by measuring the tear film thickness every 10 minutes over 1 hour. RESULTS: The average central tear film thickness of the measured population was 4.79 ± 0.88 μm. Reproducibility was very high, with an intraclass correlation coefficient of 0.97. A breakup of the tear film was observed in one subject after 14 seconds. CONCLUSIONS: Our data indicate that the human precorneal tear film can be measured with excellent reproducibility using ultrahigh-resolution optical coherence tomography. This technique may be a valuable tool in the management of dry eye syndrome.