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L.W. Jones, S. Rahman, R. Leech, T. Simpson, D. Fonn, J.G. Vehige, P.A. Simmons; Determination of Tear Meniscus Height using a Novel Method Based upon Optical Coherence Tomography . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2461.
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Purpose: Tear meniscus height is one measure of tear volume, and changes in it may correlate with the residence time of artificial tear preparations. This study sought to investigate the capability of optical coherence tomography (OCT) to measure the inferior tear meniscus height (TMH) of the tear film, following the instillation of various artificial tear products. Methods: A prospective, double-blind, randomized, cross-over study was conducted in which OCT was used to measure the TMH following the instillation of 20, 35 and 50 µl drops of Refresh Liquigel (RL), Refresh Tears (RT) and a saline control (SC). The TMH was measured frequently for 60 minutes post-insertion, with each drop size. During this time the non-invasive break up time (NIBUT) was assessed using a grid projected onto the tear-film and the time that subjects could hold their eyes open before having to blink (Maximum Interval Between Blinks - MIBB) was also determined. Results: All products produced an increase in TMH following their instillation (p<0.01). These differences were unrelated to drop size for SC (p>0.05), but were greater for the larger drop sizes for RL and RT (p<0.05). The TMH was greater for RL than SC or RT, regardless of drop size, during the first 10 minutes post-insertion (p<0.01). The time taken for the TMH to revert to baseline levels was greater for RL than for either SC or RT (p<0.05), indicating that RL was retained for almost twice as long as the other two products. The MIBB for both drop sizes was longer for RL than SC or RT and in 78% of cases a strong correlation (R > 0.85) was found between MIBB and NIBUT, regardless of the drop size. Conclusions: OCT is capable of measuring the alteration in TMH of the lower tear prism, following the instillation of products into the tear film. In this study, a product with a high viscosity was found to increase TMH to a greater extent and for a longer time period than products with a low viscosity. MIBB was significantly correlated with tear film break-up time, indicating that the MIBB is at least partially driven by tear film rupture.
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