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D. H. Szczesna, D. Iskander, D. Alonso-Caneiro, S. A. Read, M. J. Collins; Noninvasive Assesment of Tear Film Surface Kinetics. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3371.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the kinetics of tear film from noninvasive measurements of tear film surface quality (TFSQ) during suppressed blinking conditions.
Twenty two normal subjects and twelve subjects with dry eye, aged from 20 to 68 years were recruited for this study. Noninvasive measurements included dynamic-area high speed videokeratoscopy (HSV), dynamic wavefront sensing (DWS), and lateral shearing interferometry (LSI). The dynamic-area HSV relies on measuring changes in the recorded Placido disc pattern projected onto the cornea. In DWS, temporal changes of higher order aberrations (HOA), total comatic terms (ComaV, and ComaH) and the Zernike polynomial RMS fit error were used as indicators of TFSQ. In LSI, temporal changes in the frequency characteristics of interferograms were used as a TFSQ indicator.
A distinct tear film build-up phase was observed in over 99% of measurements in LSI, from 15% to 24% of measurements in HSV and from 24% to 50% of measurements in techniques based on DWS. The tear film stability phase, thinning phase as well as the tear film break-up (if it occurred) were observed with all instruments. Additionally, with LSI, a two-stage build-up time has been observed in both normal and dry eye subjects. The figure presents an example of estimated tear film surface kinetics for a dry eye subject using LSI. The detection threshold of break-up has been established based on statistics from measurements of TFSQ in 18 normal subjects during natural blinking. For the majority of dry eyes the tear film stability phase was shorter than in normal eyes or it was not observed.
The LSI technique is able to characterize up to five different phases of tear film surface kinetics that include: (1) initial fast tear film build-up phase, (2) further slower tear film build-up phase, (3) tear film stability, (4) tear film thinning, and (5), after a detected break-up, subsequent tear film deterioration. HSV as well as the DWS are suitable for characterizing the last two phases of tear film kinetics.
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