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J. S. Lee, A. Salapatek, P. Patel, F. Soong; Comparison of Non-Invasive Tear Break Up Times (NIBUT) Assessed With Video-Corneal Topography to the Standard Invasive TBUT as Studied in Patients After Exposure to Low Humidity Environment (LHE). Invest. Ophthalmol. Vis. Sci. 2009;50(13):525.
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To evaluate the effectiveness of utilizing video corneal topography as a measure of NIBUT as compared to standard fluorescein TBUT measures.
The tear break up times in 8 dry eye patients (60 observations) were evaluated with both standard fluorescein (TBUT) and video-corneal topography (NIBUT) methods, pre- and post-exposure to LHE, with measures repeated 3 times. The measurement of NIBUT involved monitoring placido disc concentric mire reflections after a blink for any distortion in mires or image. Video-recording of this technique increases its sensitivity since it allows for a review of mire reflections for first occurrence of distortion compared to detection during live assessment. The video capture of this measure by MedmontTM topographer and software resulted in timed images. These images were reviewed to calculate the time between the blink (and subsequent refreshed concentric mire reflection) and the first occurrence of mire distortion to determine NIBUT. Factors including tear meniscus, lid tautness and eyelashes also influenced the assessment of concentric mire distortion. Pearson correlation analyses and curve-fitting were performed to compare the TBUT and NIBUT data.
With both TBUT and NIBUT, there was a reduction in tear break-up time after exposure in LHE (median change TBUT:-1.84s, p<0.05; NIBUT:-0.74s, n.s.). However, 90% of the time, NIBUT was larger than TBUT by 1.85±1.48s. There was a strong correlation between TBUT and NIBUT (r=0.74, p<0.0001) where curve-fitting revealed an exponentially larger NIBUT value for matched TBUT values.
Both the NIBUT and invasive TBUT results were comparable. However, NIBUT with video corneal topography is a non-invasive method of measuring tear break-up time without instillation of fluid or dyes. Utilization of this non-invasive measure may prove valuable in the repeated assessment of tear break-up time in a LHE chamber model and testing of dry eye therapies. More clinical evaluation and analysis of this technique is warranted.
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