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S.J. Kendig, C. Amos; The Effects Of Lens Care Products On The Dehydration Of Hydrogel Contact Lenses Measured By Dynamic Vapor Sorption . Invest. Ophthalmol. Vis. Sci. 2004;45(13):1545.
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Purpose: To determine the dehydration characteristics of five commercially available contact lenses from FDA material groups I and IV (Focus 1–2 Week®, Acuvue 2®, Cibasoft®, Focus Dailies®, and SofLens 66® ) after equilibrating with three commercially available multipurpose contact lens soaking solutions (ReNu MultiPlus®, OptiFree Express® and Complete®), one investigational solution (AQuifyTM MPS) and Softwear® saline (as control). Methods: The Dynamic Vapor Sorption (DVS) apparatus (Surface Measurements Systems Ltd) was used to monitor the dehydration of hydrogel contact lenses by measuring the mass of a lens as it is exposed to controlled humidities. Lenses are exposed to relative humidity ≥ 95% for 15 minutes and quickly stepped down to 50% RH for an additional 60 minutes. The environmental temperature is controlled at 34 ± 0.3° C throughout the test, to mimic on–eye conditions. During the dehydration process, initial mass, final mass, rate of weight loss and the percent water contents are identified for each lens. Results: Lenses undergo dehydration at two distinctly different rates described by an exponentially decaying curve. The maximum dehydration rate occurs immediately following the step down to 50% relative humidity and is linear. After an inflection point an almost flat line steady state equilibrium is reached where further dehydration continues at a greatly reduced level. The initial linear dehydration rates vary between lens materials but are not affected by solutions. The steady state equilibrium water content levels are affected by solutions and particularly by AQuifyTM MPS that had steady state levels that were 50% higher than the other lens care products. Conclusions: AQuifyTM MPS appeared to limit the dehydration loss of hydrogel lenses which may help to improve contact lens performance.
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