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Clayton J Radke, Young Hyun Kim, Sarah M Yi, Kayla H Panora, Jessica W Yuen, Wing Li, Meng C Lin; Minimal Effect of Evaporation on Ocular Surface Temperature with Contact-lens Wear. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6345.
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© ARVO (1962-2015); The Authors (2016-present)
Li et al. (2017 ARVO) showed correlation between ocular surface cooling rate (OSCR) and soft contact-lens (CL) wear dryness but alluded no correlation with tear-film evaporation rate. The purpose of this study was to examine OSCR in local and overall regions of interest (ROI) and examine the theoretical model of Dursch et al. (2018 OVS) to understand if evaporation is the predominating factor to CL wear dryness for asymptomatic (ASx) and symptomatic (Sx) CL wearers.
Nine ASx (Age (SD) = 21.9 (2.3)) and 9 Sx (Age (SD) = 25.2 (3.2)) CL wearers were recruited to participate in the study. Subjects were seen for one visit and wore Biofinity® CL (CooperVision, Inc., Pleasanton, CA). Histories of ocular surface temperature (OST) were measured before CL wear, after lens insertion, and 6 hours after CL wear using FLIR A655sc Infrared Thermographer. Operator-determined cornea was chosen as overall ROI, hot and cold local ROI were determined with customized Matlab script, and OSCRs were determined by line of best fit. Analysis of variance was done to assess the 95% confidence interval. Evaporative rate of tear in respect to water was varied in the model of Dursch et al. to understand the effects of evaporation on the OST.
Table 1 displays the mean and p-values for the calculated OSCRs. P-values assess the significance in mean differences at different measuring time points. There was statistical significance in rate difference in ASx without CL wear and after 6-h CL wear. Fast cooling and slow cooling localized ROI had statistically significant differences in the OSCRs for both groups (p < 0.05) for any given time point. Theoretical model shows ~0.05 °C difference between no and maximum evaporation while subjects showed change in OST to be at least a magnitude larger than the model.
OSCRs for fast and slow cooling ROI are significantly different for all lens wearers; seemingly supporting the hypothesis of localized evaporative cooling. However, OSCR slows down with lens wear for ASx group but remains constant with Sx group, and theoretical model predicts minimal OST change due to evaporation. These observations suggest that increased evaporative cooling is not a predominant factor responsible for CL wear dryness.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Table 1: Mean ocular surface cooling rates and p-values for local and overall cooling regions for asymptomatic and symptomatic groups
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