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D. Welch, G.W. Ousler, M.B. Abelson; An Approach to a More Standardized Method of Evaluating Tear Film Break-Up Time . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2485.
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Purpose: Historically, the technique for evaluating tear film break-up time (TFBUT) has lacked consistency. Large and varying amounts of sodium fluorescein (up to 50 µl) were used, times were determined by counting aloud and the instruments with which the tear film is evaluated were less sophisticated. It has been shown that such techniques yield varying results. This study examines the variability of TFBUT when standardized, well-controlled techniques are used in a dry eye population. Methods: Twenty-seven (27) subjects diagnosed with dry eye underwent TFBUT assessments on Days 0, 7 and 14 by a single investigator. One (1) micro-liter of non-preserved, 2% sodium fluorescein was instilled using an EagleTM E2 pipette. TFBUT was defined as the time between the opening of the eyelids and the first appearance of a growing micelle. The slit-lamp magnification was set at 10X, the background illumination intensity was kept constant and a Wratten #12 filter was used to enhance observation of the tear film over the entire cornea. All evaluations were captured with a digital imaging system that incorporates an on-screen timer, allowing for precise determination of TFBUT. Mean TFBUT and the associated standard deviations were calculated for each patient over the three visits. Further, the standard deviations as a percentage of mean TFBUT was calculated for each patient. The subjects were stratified into 4 groups (1-2, 2-3, 3-4, and 4-5 mean TFBUT in seconds) in order to evaluate the relationship between mean TFBUT standard deviation. Results: The mean standard deviation across all subjects was 0.767s. The mean standard deviations for the 4 groups were 0.37, 0.68, 0.95, and 1.23 seconds, respectively. The standard deviations as a percentage of mean TFBUT were 22.2%, 26.5%, 28.1%, and 26.0%, respectively. Conclusions: The data suggests that when TFBUT is determined with well-controlled and standardized techniques, consistent measurements are observed.
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