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Holly Irene Lorentz, Stephanie Recker, Chuck Shi, James J Mun, Anne Marie Salapatek, Fiona Soong; A Low and High Humidity Controlled Environmental Exposure Model (EEC) Model: A Highly Specific and Sensitive Model to Measure In Vivo CL dehydration . Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):6108.
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© ARVO (1962-2015); The Authors (2016-present)
An investigational, proof of concept study, to evaluate the impact of low and high controlled humidity environments on contact lens (CL) dehydration.
10 non-symptomatic adapted CL wearers were screened and randomized to a treatment sequence of two different CL materials (etafilcon A [ETA] and senofilcon A [SEN]) worn at four EEC visits in which the environmental conditions were set to either 10±3% RH or 50±5% RH, an air flow of 2-5ft/sec and a temperature of 23±3°C. Prior to entering the EEC, randomized CLs were worn briefly (<1 min) by the subjects and then removed so their baseline wet weight could be measured using gravimetry. A new pair of randomized CLs was then inserted prior to the subjects entering the EEC for 150min to visually task on a digital screen. Upon exit from the EEC, all worn CLs were removed directly from the eye and their post-EEC wet weight measured via gravimetry. Following wet weight measurements, CLs were fully dehydrated and dry weight measured. CL water content determined according to ISO standards.
ANCOVA analysis of the main variables, revealed statistically significant differences (p<0.002) in MCFB CL water content when lenses were worn in the EEC under RH10% when compared to RH50%. Similarly, statistically significant differences between SEN and ETA MCFB CL water content were also found in the EEC (p<0.002). When looking at the individual treatment regimens in the ANCOVA analysis, the greatest MCFB decreases in water content were seen for ETA RH10% (LSMeans -4.90%±0.23%) when compared to ETA RH50% (LSMeans -3.08%±0.23%), p<0.0001. Statistical differences in LSMeans were also seen between 10%RH ETA and 10%RH SEN (p=0.047) and between 50%RH ETA and 50% SEN (p=0.001).
In vivo contact lens dehydration can be examined in the controlled humidity EEC model; the low humidity EEC elicits more CL dehydration than high humidity EEC conditions, especially for ETA. In this small sample, the controlled humidity EEC model was able to detect small differences in water content between different lens materials as well as in different humidity conditions using the ANCOVA model.
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