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Stephanie Wong, Edward Lum, Aniol Planaguma Cornella, Paul J Murphy, Lyndon William Jones; Surface temperature change in soft contact lenses: an in vitro study. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3097.
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Evaporative water loss from a contact lens (CL) influences daily wear comfort. During a blink a CL undergoes a cycle of warming and cooling which is repeated during the day and which may influence this evaporative water loss. This response may be dependent on lens material and water content (WC). This study investigates the effects of WC and material type on the forced heating of soft CL.
An infrared thermal camera (FLIR A655sc) was used to measure surface temperature (ST) change of 2 silicone hydrogel CL: (Dailies Total1 [DT1] - 33%WC, Acuvue Oasys - 38%WC) and 3 hydrogel CL (SofLens 38 - 38.6%WC, 1-Day Acuvue Moist - 58%WC, Biotrue daily - 78%WC). Each CL (-3.00D BVP) acclimatised to ambient temperature (25-26°C) and humidity (39-48%) before being placed on a model eye for 10 minutes. The model eye comprised a mini-scleral (7.70mm BOZR) glued onto a 20mm diameter heated dome (32.7±0.6°C). This combination was painted matt black. ST was recorded at the centre of the CL. Measurements over time and between CL types were compared using repeated measures ANOVA and post-hoc Games-Howell test.
Significant changes in ST occurred for all lens types (p<.001). All CL passed through periods of rapid warming from room temperature on initial placement on model eye. After peak warming, all CL underwent gradual cooling due to water evaporation from CL surface. The rate of ST change varied with lens type (p<.001). The rate of ST cooling was fastest in Oasys (-1.9°C/min), followed by DT1 (-1.6°C/min), SofLens 38 (-1.5°C/min), Biotrue (-1.1°C/min), and Moist (-0.95°C/min). Upon reaching minimum ST, and a short stabilization period, ST increased (p<.001) for SofLens 38 (+0.47°C/min) and Oasys (+0.46°C/min). DT1 showed a trend toward ST increase (+0.15°C/min). ST remained stable for Moist and Biotrue over the remaining test period.
There was an inverse relationship between the rate of surface cooling and material WC. Subsequent increases in central lens ST occurred only in low WC lens types and were unrelated to material type. These findings suggest that evaporation influences the rate and extent of temperature change, and that this evaporative effect is limited by available water in the lens. Further investigations are required for other CL types and longer periods of forced CL heating.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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