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H. Liu, C. Begley, S.P. Srinivas, G. Wilson; Tear Break-Up: What Can Spatial Reoccurrence Tell Us About the Mechanism? . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2479.
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Purpose: To investigate the spatial reoccurrence of the tear break-up domain (TBUD) over the corneal surface to gain insights into the mechanisms initiating tear break-up. Methods: Tear break-up was induced by keeping one eye open for as long as possible. TBUD was quantified by video imaging of tear film fluorescein staining in 12 normal subjects. Analog images were digitized and tear fluorescence patterns were quantified to obtain the TBUD location and area, which was a percent of the exposed corneal surface. The overlap of TBUDs among 3 successive trials 5 minutes apart, was computed by a MATLAB program. Results: The average percent TBUD of the exposed corneal surface measured just before the blink among the 3 trials was 26.8%±13.4% (range: 4.4% to 49.9%) and the average overlap was 7.3%±6.7% (range: 0.04% to 21.60%). The correlation between the average area and overlap of TBUD in 3 trails was high (Spearman’s: r=0.94, p<0.0001) with greater overlap occurring with increasing areas of TBUD. Compared to the probability of overlap by unrelated points, the actual overlap of 3 TBUD trials was only slightly greater (average of 4%±3.12%; range 0.03% to 10.37%). TBUD locations appeared more often in the superior, inferior and nasal areas than in the other part of the cornea. Conclusions: Keeping the eye open as long as and possible yielded a relatively small area of TBUD overlap in 3 successive trials. This suggests that the underlying cause of tear break-up may not be due to surface abnormalities in the epithelium or bound mucin layer, but rather to dynamic interfacial forces perhaps influenced by the lipid layer. The most common locations of TBUDs could be attributed to lid-tear film interactions.
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