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Carolyn G. Begley, Adam Winkeler, Jayoung Nam, Richard Braun, Larry Thibos, Arthur Bradley; Spatiotemporal Changes in Tear Film Break-up Analyzed by Two Independent High-Resolution Imaging Techniques. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4254.
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The purpose of this study was to investigate the development and spatial patterns of tear film breakup (TBU) by measuring changes in relative tear film thickness using two simultaneous, independent, and high-resolution imaging techniques.
A slit-lamp biomicroscope was custom modified to emit simultaneous widefield blue and near infrared light for fluorescence (FL) and retroillumination (RI) imaging. Two high-resolution synchronized cameras simultaneously collected images of local spatial changes in TBU following instillation of fluorescein dye and 0.5% proparicaine (5 subjects). Images were registered, select breakup areas were evaluated, and FL and RI intensity changes in these areas were mapped over time (custom MATLAB programs). Spatiotemporal changes in tear film thickness were compared, and tear film thinning rates within areas of TBU were estimated using published tear film thickness values (King-Smith et al, 2004).
Over time, FL intensity decreased reaching a minimum within areas of TBU, suggesting a full thickness break. The mean (±SD) time to minimum FL intensity was 12.6±7.6 sec, with an average thinning rate of 19.8±11.2 µm/min given an initial 3μm thick tear film. Plots of the slope of the FL image (derivative) agreed well with RI image intensity changes when TBU was present (Himebaugh et al, 2003). Conversely, as the figure shows, in areas of corneal FL staining, FL intensity changed little with time after a blink even when RI images indicated the development of TBU.
These two high-resolution methods for evaluating TBU show good agreement and thus can be used to independently estimate relative spatiotemporal changes in tear film thickness. The RI technique allows for high-resolution, noninvasive tracking of TBU over areas of corneal FL staining.
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