We report the results of some recent experiments to visualize tear film dynamics. We then study a mathematical model for tear film thinning and tear film breakup (TBU), a term from the ocular surface literature. The thinning is driven by an imposed tear film thinning rate which is input from in vivo measurements. Solutes representing osmolarity and fluorescein are included in the model. Osmolarity causes osmosis from the model ocular surface, and the fluorescein is used to compute the intensity corresponding closely to in vivo observations. The imposed thinning can be either one-dimensional or axisymmetric, leading to streaks or spots of TBU, respectively. For a spatially-uniform (flat) film, osmosis would cease thinning and balance mass lost due to evaporation; for these space-dependent evaporation profiles TBU does occur because osmolarity diffuses out of the TBU into the surrounding tear film, in agreement with previous results. The intensity pattern predicted based on the fluorescein concentration is compared with the computed thickness profiles; this comparison is important for interpreting in vivo observations. The non-dimensionalization introduced leads to insight about the relative importance of the competing processes; it leads to a classification of large vs small TBU regions in which different physical effects are dominant. Many regions of TBU may be considered small, revealing that the flow inside the film has an appreciable influence on fluorescence imaging of the tear film.

中文翻译：

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关于泪膜破裂（TBU）：动力学和成像。

我们报告了一些最近实验的结果，以可视化泪膜动态。然后，我们研究了泪膜变薄和泪膜破裂（TBU）的数学模型，这是眼表文献中的一个术语。变薄是由强加的泪膜变薄率驱动的，该变薄率是从体内测量输入的。模型中包含代表渗透压和荧光素的溶质。渗透压引起模型眼表面的渗透，并且荧光素用于计算与体内观察密切对应的强度。施加的细化可以是一维的，也可以是轴对称的，分别导致 TBU 的条纹或斑点。对于空间均匀（平坦）的薄膜，渗透作用将停止变薄并平衡由于蒸发而损失的质量；对于这些空间相关的蒸发曲线，TBU 确实发生，因为渗透压从 TBU 扩散到周围的泪膜中，这与之前的结果一致。将基于荧光素浓度预测的强度图案与计算的厚度分布进行比较；这种比较对于解释体内观察结果很重要。引入的无量纲化可以让我们了解竞争过程的相对重要性；它导致对大 TBU 区域和小 TBU 区域进行分类，其中不同的物理效应占主导地位。TBU 的许多区域可能被认为很小，这表明膜内的流动对泪膜的荧光成像有相当大的影响。