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C. Purslow, J. Wolffsohn; The Application of Infrared Thermography to Assess Ocular Surface Temperature During Blinking . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1941.
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© ARVO (1962-2015); The Authors (2016-present)
To examine post–blink changes in ocular surface temperature (OST), using dynamic thermal imaging, and to relate such findings to tear flow dynamics and underlying ocular anatomy.
Dynamic ocular thermography was used to record OST for 8 seconds following a blink in the right eyes of 169 healthy subjects. Monochrome thermal images were analysed at 30Hz, and OST was recorded from 23 selected points across the ocular surface. Surface contour plots were constructed to show dynamic changes in OST during the post–blink period. Two–way repeated measures ANOVA was used to compare the effects of time and location on OST. Curve–fitting and regression modelling was used to analyse the dynamic changes in post–blink OST.
OST decreased in all areas across the ocular surface during the post–blink period, producing a characteristic thermal profile. It was observed that thermal contours were not initially concentric: after 1s concentric contours became clear with long axis horizontal. The magnitude of post–blink cooling differed significantly between areas (p<0.0001): the mean decrease at geometric centre was 0.9±0.5°C. Positon and time of measurement were statistically significant influences on recorded OST (p<0.0001 and p<0.001 respectively), with the more peripheral areas showing least change with time (p<0.001). Throughout the post–blink period, the central area remained significantly coolest, and the nasal area warmest (p<0.001). Rates of cooling fitted to exponential decay curves, showing an initial rapid phase of cooling followed by a more gradual decline. Rate constants from decay functions for each area were compared (p<0.0001): the central area cooled at a significantly faster rate; nasal and superior areas were similar; inferior and temporal areas cooled most slowly.
The rate of post–blink cooling varies significantly across the ocular surface. Observations can be explained using established principles of tear flow dynamics and thinning. Temperature changes recorded initially reflect the tear fluid gathering in both menisci and being drawn nasally towards the punctae. The resulting thermal profile reflects natural tear flow and drainage, and the influence of underlying ocular anatomy. Dynamic ocular thermography potentially offers a non–invasive method for assessing tear flow dynamics in other cohorts, such as contact lens wearers and dry eye patients.
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