Repeated measurements of dynamic tear distribution on the ocular surface after instillation of artificial tears

PURPOSE. To determine the repeatability of real-time optical coherence tomography (OCT) measurements of tear film thickness (TFT) and variables of tear film menisci. METHODS. Forty eyes were imaged with a custom-built, real-time OCT to obtain heights, curvatures, and cross-sectional areas of upper and lower tear menisci simultaneously. The central TFT was indirectly determined as the difference between the combined thickness of the central cornea and tear film and the true corneal thickness obtained after instillation of artificial tears. Dynamic tear distribution was determined by OCT imaging immediately and 5, 20, 40, and 60 minutes after tear instillation. Measurements taken after two blinks of one eye at each visit were repeated on the next day. Measurements from the companion eye were made on separate days. RESULTS. There were no significant differences between the two measurements of each variable made on consecutive days. At baseline, upper tear meniscus variables were strongly correlated with the comparable lower meniscus variables. However, there were no significant correlations between TFT and any tear meniscus variable. Immediately after instillation of artificial tears, all measured variables increased significantly. TFT, upper and lower menisci heights, and upper meniscus area remained elevated for at least 5 minutes. In addition there were significant correlations between TFT and the lower tear meniscus height and area. CONCLUSIONS. The custom-built OCT showed good repeatability and holds promise in measuring the dynamic distribution of artificial tears on the ocular surface.