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Michael Watson, Keith Jeffrey Lane, Endri Angjeli, Peter Corcoran, John David Rodriguez, George W Ousler; Ocular Surface Thermal Imaging in Normal and Dry Eye Subjects. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2858.
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© ARVO (1962-2015); The Authors (2016-present)
To examine inter-blink ocular surface temperature change between normal and dry eye subjects, using a FLIR A655sc thermal camera.
20 subjects participated: 15 normal controls with no history of ocular surface disease nor diagnosis of dry eye, no symptoms of ocular discomfort, and no history of artificial tear use, and 5 dry eye patients with current symptoms of ocular dryness. Preliminary analysis of all videos was done using an internally developed software program, which tracks the eye and monitors temperature parameters across a 16-region grid that overlays the cornea. Cooling rate is the change in corneal temperature (all 16 regions) during an inter-blink interval (IBI), modeled as a linear regression. Mean cooling rate is the average of all linear regressions over all IBIs. Percent change in temperature within an IBI was calculated as (1-TFinal/TInitial). Each video was between 60 and 120 seconds, taken in a room with a controlled environment. Only IBIs greater than 2 seconds were analyzed to eliminate rapid flutter blinks, in which no thermal changes between blinks occurred.
Mean cooling rate (oC/sec over blink interval) and mean percent temperature change were significantly different between our populations of normal and dry eye patients (p<0.05). Mean cooling rates were 0.035oC/sec for normal patients and 0.152oC/sec for dry eye subjects. Mean percent temperature drop within each IBI was 0.336% for normal patients, and 0.518% for dry eye subjects.
Within an IBI, dry eye subjects had a greater rate of decrease, and a greater overall percent decrease in temperature. The former finding may be due to increased rates of tear film evaporation, and/or may reflect an inability of the tear film to buffer cooling from extremal air flow. The latter finding may be due to a diminished ability of the dry eye to respond to critical temperature drops via blink. The ability of infrared technology to differentiate dry eye subjects, as a nearly 5-fold difference in cooling rate compared to normals, shows its potential as a screening tool and/or clinical endpoint.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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