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Deborah Awisi-Gyau, Carolyn G Begley, Richard J Braun, Rayanne A Luke, Anna F Tichenor, Peter Ewen King-Smith; Characterization of development and Repeatability of Tear breakup shapes. Invest. Ophthalmol. Vis. Sci. 2020;61(7):1392.
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© ARVO (1962-2015); The Authors (2016-present)
Tear breakup(TBU) plays a critical role in dry eye disease(Craig,Oc Surf,2017).Patterns of TBU are associated with dry eye subtypes and symptoms(Yokoi et al.,Am JOphthalmol,2017).In this study, we quantify the origin,development of shapes, areas, locations of TBU, their repeatability and TBU thinning rates in normal subjects to understand the natural process of TBU previous to DED.
Fluorescein was instilled into lefteye of 15normal subjects and kept open as long as possible in 3consecutive Sustained TeAR Exposure trials and recorded. Frames were extracted from videos of the tearfilm and the first three areas of TBU identified. Properties of location,shape, including area, orientation and circularity were quantified and thinning rate was calculated. Areas of TBU were categorized as spots(circularity>0.6) and streaks(circularity<0.6) by their shape at end of each trial.Repeatability of areas of TBU over the 3 trials were determined.
45 TBU cases were examined.Average percent area(±SD) of TBU in superior, central and inferior of the exposed corneal surface were 3.47%(3.97), 4.33%(3.03) and 2.91%(3.01)respectively. Average(±SD)percentage overlap between the 3 consecutive trials in superior, central and inferior regions were 0.62%(1.44), 0.62%(1.28)and 0.31%(0.72)respectively. Almost all TBU(96%) cases started as spots and 60% grew into streaks(Fig 1).18 and 27 cases were identified as spots and streaks respectively. Range of thinning rates(reduction in pixel intensity) for all areas of TBU was 0.9%PI/sec to 13.9 %PI/sec, with a median rate of 5.1%PI/sec for streaks and 2.7%PI/sec(Fig 2) for spots.Spots tended to have a smaller area, 0.07mm2 (0.10) compared to streaks, 0.47mm2(0.53). For streaks identified, 10 were oriented horizontally(0 to 300),8 were oblique(30 to 600) and 10 were vertical(60 to 900).
TBU in these normal subjects occurred in all corneal regions with relatively low repeatability in location. Most TBU areas began as small spots,with streaks expanding from spots in all orientations. Thinning rates suggest evaporation as a mechanism involved in the development of most areas of TBU, but more rapid(<4sec)TBU may also involve surface tension effects.
This is a 2020 ARVO Annual Meeting abstract.
Change in circularity of TBU streaks from beginining to end of trial
Thinning rates in streak and spot TBU
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