Effect of blinking on tear dynamics

PURPOSE. Optical coherence tomography (OCT) was used to study the impact of blinking on tear dynamics. METHODS. One eye of 21 subjects was imaged at the same time of day on two consecutive days. Dimensional information of the tear film and of the upper and lower tear menisci during normal and delayed blinking were obtained from OCT images using custom software. Digital camera images were used to measure eyelid length and ocular surface area for tear volume estimation. RESULTS. No significant changes in any measured variable occurred between the two repeat visits. During normal and delayed blinking sessions, the tear film thickness increased significantly after each blink (P < 0.05) and then decreased (P < 0.05) during the open-eye period. For normal blinks, the tear meniscus did not change significantly during blinking or during the open-eye period. Except for upper tear meniscus curvature, all other parameters of tear menisci during delayed blinks were higher than those measured during normal blinks (P < 0.05). For delayed blinks, the lower tear meniscus height decreased after the blink (P < 0.05). Also for delayed blinks, the height and area of both upper and lower tear menisci significantly increased during the open-eye period. The total estimated tear volume on the ocular surface was greater during the delayed blinks (P < 0.01), and most of the volume was located in the lower tear meniscus (P < 0.01). CONCLUSIONS. OCT is a promising tool for studying the impact of blinking on tear dynamics. Tear distribution is dynamically balanced and consistent during normal blinking, but it becomes altered during delayed blinking.