Effects of Temperature and Blinking on Contact Lens Dehydration of Contemporary Soft Lens Materials Using an In Vitro Blink Model
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PURPOSE: The purpose of this study was to evaluate the effects of temperature and blinking on contact lens (CL) dehydration using an in vitro blink model. METHODS: Three silicone hydrogel (delefilcon A, senofilcon A, and comfilcon A) and two conventional hydrogel (etafilcon A and omafilcon A) CL materials were evaluated at 1 and 16 hours. The water content (WC) of the CLs was measured using a gravimetric method. Lenses were incubated on a blink model, internally heated to achieve a clinically relevant surface temperature of 35°C. An artificial tear solution (ATS) was delivered to the blink model at 4.5 µL/min with a blink rate of 6 blinks/min. A comparison set of lenses were incubated in a vial containing either 2 mL of ATS or phosphate-buffered saline (PBS) at 35°C. RESULTS: Increasing temperature to 35°C resulted in a decrease in WC for all tested CLs over time (P ≤ 0.0052). For most CLs, there was no significant difference in WC over time between ATS or PBS in the vial (P > 0.05). With the vial system, WC decreased and plateaued over time. However, on the blink model, for most CLs, the WC significantly decreased after 1 hour but returned toward initial WC levels after 16 hours (P > 0.05). CONCLUSIONS: The reduction in WC of CLs on the eye is likely due to both an increase in temperature and dehydration from air exposure and blinking. TRANSLATIONAL RELEVANCE: This study showed that the novel, heated, in vitro blink model could be used to provide clinical insights into CL dehydration on the eye.
