Dynamics of Fluorescent Imaging for Rapid Tear Thinning

Abstract

A previous mathematical model has successfully simulated the rapid tear thinning caused by glob (thicker lipid) in the lipid layer. It captured a fast spreading of polar lipid and a corresponding strong tangential flow in the aqueous layer. With the simulated strong tangential flow, we now extend the model by adding equations for conservation of solutes, for osmolarity and fluorescein, in order to study their dynamics. We then compare our computed results for the resulting intensity distribution with fluorescence experiments on the tear film. We conclude that in rapid thinning, the fluorescent intensity can linearly approximate the tear film thickness well, when the initial fluorescein concentration is small. Thus, a dilute fluorescein is recommended for visualizing the rapid tear thinning during fluorescent imaging.

Mechanistic determination of tear film thinning via fitting simplified models to tear breakup

“…Clinically, this is defined as the first dark area that is observed in the fluorescent (FL) TF following instillation of fluorescein dye. 1 Various mechanisms are thought to cause di erent types of TBU: evaporation [2][3][4] causes relatively slow thinning, 5 and rapid thinning may be explained by Marangoni-driven tangential flow, 6 or plausibly, dewetting in cases of circular TBU. 7,8 Here, we use the phrase tangential flow to mean flow along the eye.…”

“…4,14 The e ects of evaporation and the Marangoni e ect on TBU have been studied extensively 4,15 and modeled separately; [16][17][18][19] only recently have they been explored in combination to explain breakup occurring on an intermediate time scale. 6 This intermediate time scale allows us to study breakup for which lipid-driven Marangoni flow alone may be too fast, but evaporation alone is too slow to explain. Zhong et al 6 developed a partial di erential equation (PDE) model with one spatial variable that incorporated both mechanisms.…”

“…6 This intermediate time scale allows us to study breakup for which lipid-driven Marangoni flow alone may be too fast, but evaporation alone is too slow to explain. Zhong et al 6 developed a partial di erential equation (PDE) model with one spatial variable that incorporated both mechanisms. Luke et al 20 fit full thickness-TBU data from fluorescent (FL) images from healthy subjects with a rescaled version of the Zhong et al 6 model.…”

“…Zhong et al 6 developed a partial di erential equation (PDE) model with one spatial variable that incorporated both mechanisms. Luke et al 20 fit full thickness-TBU data from fluorescent (FL) images from healthy subjects with a rescaled version of the Zhong et al 6 model. The authors studied breakup occurring on the intermediate time scale of 1-8 s postblink.…”

Mechanistic determination of tear film thinning via fitting simplified models to tear breakup

“…Clinically, this is defined as the first dark area that is observed in the fluorescent (FL) TF following instillation of fluoresecein dye 1 . Various mechanisms are thought to cause di erent types of TBU: evaporation [2][3][4] causes relatively slow thinning 5 , and rapid thinning may be explained by Marangoni-driven tangential flow 6 or, plausibly, dewetting in cases of circular TBU 7,8 . The Marangoni e ect drives outward flow at the aqueous/lipid interface induced by shear stress as a result of a lipid concentration gradient 9,10 .…”