Tear Breakup (TBU) Analysis with Fluorescence (FL) and Thermal (TH) imaging

Abstract

Purpose : Analyzing TBU with two imaging modalities, FL and TH, has the potential to greatly aid determination of mechanism and dynamics of TBU in the tear film (TF). We have recently shown that FL imaging can be used to quantify mechanisms of TBU for individual and groups of subjects. TH imaging can augment that capability with independent inputs that refine parameter identification in TBU.

Methods : Following instillation of 2µl of 2% FL, 10 subjects kept one eye open for as long as possible, a procedure known as sustained tear exposure (STARE) while the TF was simultaneously imaged with FL and TH cameras. We extracted the FL and TH image data from manually chosen TBU regions. The data were fit with the ordinary differential equation (DE) models for the TF thickness, osmolarity and FL concentrations using parameters representing evaporation rate amd variable tangential flow (strain) rate. The TF equations are coupled to a partial DE model for the interior eye temperature. Initial FL concentration and localized TF thickness were estimated as in previous work (Wu et al IOVS 2015, 56:4211; Luke et al Bull Math Biol 2020, 82:71). All programs were custom using Julia and/or Matlab.

Results : Preliminary results produce multiple usable instances of TBU from each subject (e.g. Figs. 1 & 2). Evaporation rates and other fell within experimental ranges. Temperature differences across the tear film were tiny, as in previous results (e.g., Dursch et al OVS 2018, 95:5–12). Just four parameters (evaporation rate, convective cooling, & 2 for flow) appear to be sufficient to fit the two types of data well.

Conclusions : FL intensity decay, together with temperature decay at the TF surface, can yield quantitative insight into TBU dynamics and parameters. Since these quantities cannot currently be measured directly, these results provide theoretical estimates driven by data which provide a better understanding of the sensory stimuli presented to the ocular surface during TBU. Quantifying these stimuli may lead to better understanding of sensory response.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Fig 1: Sample math model FL intensity answers (I(t)) with experiment (I_exp(t)). The thickness (h), osmolarity (c) and FL concentration (f) are also shown, all as functions of time t.

 

Fig 2: Eye temperature results for the same case as Figure 1. The TF/cornea interface is located at y=0. T₀ & T(h,t) are the corneal and TF surface temperatures, respectively.