Tranoudis Ioannis, Efron Nathan
Department of Optometry and Neuroscience, University of Manchester Institute of Science and Technology, P.O. Box 88, Manchester M60 1QD, UK.
Cont Lens Anterior Eye. 2004 Sep;27(3):115-31. doi: 10.1016/j.clae.2004.03.001.
The parameters of soft contact lenses may alter during wear. A series of clinical and laboratory experiments were conducted in order to examine the parameter stability of eight soft contact lenses manufactured from different materials. The following materials (and nominal water contents) were used: HEMA/VP 40%, HEMA/VP 55%, HEMA/VP 70%, VP/MMA 55%, VP/MMA 70%, HEMA 40%, HEMA/MAA 55% and HEMA/MAA 70% (HEMA: 2-hydroxy-ethyl methacrylate, VP: vinyl pyrrolidone, MMA: methyl methacrylate, MAA: methacrylic acid). Two lenses from each of the eight soft contact lens groups were used in experiments concerning the parameter stability. Six subjects were fitted with lenses for 1 day. Verification of back optic zone radius, total diameter, back vertex power, centre thickness and water content was undertaken at 20 degrees C. In vitro measurements of water content, oxygen transmissibility, total diameter and back optic zone radius were taken at 35 degrees C before lens fitting and after 6h of lens wear. Distortion, discolouration and lens quality were assessed before and after lens wear. When the temperature was raised from 20 to 35 degrees C, a significant reduction in lens water content for all the lens types was observed, as well as a significant reduction in total lens diameter for the majority of the lens types. Water content, oxygen transmissibility, total diameter and back optic zone radius of all the lens types reduced, following a 6h open eye wearing period. For the majority of the lens types, these changes were found to be statistically significant. Distortion, discolouration and quality of the lenses remained unchanged throughout the study with the exception of the HEMA/MAA 70% lens. Correlating a number of parameters generated in this study, gave the following conclusions. High water content materials exhibit a low relative change in oxygen transmissibility following a 6h wear period. Soft contact lens dehydration leads to a decrease in oxygen transmissibility and total diameter, following a 6h wear period. These results will assist practitioners in predicting the alterations that occur in soft contact lens parameters and oxygen performance as a result of lens wear.
软性隐形眼镜的参数在佩戴过程中可能会发生变化。为了检测8种由不同材料制成的软性隐形眼镜的参数稳定性，进行了一系列临床和实验室实验。使用了以下材料（及标称含水量）：甲基丙烯酸羟乙酯/乙烯基吡咯烷酮40%、甲基丙烯酸羟乙酯/乙烯基吡咯烷酮55%、甲基丙烯酸羟乙酯/乙烯基吡咯烷酮70%、乙烯基吡咯烷酮/甲基丙烯酸甲酯55%、乙烯基吡咯烷酮/甲基丙烯酸甲酯70%、甲基丙烯酸羟乙酯40%、甲基丙烯酸羟乙酯/甲基丙烯酸55%和甲基丙烯酸羟乙酯/甲基丙烯酸70%（甲基丙烯酸羟乙酯：2-羟基乙基甲基丙烯酸酯，乙烯基吡咯烷酮：乙烯基吡咯烷酮，甲基丙烯酸甲酯：甲基丙烯酸甲酯，甲基丙烯酸：甲基丙烯酸）。8组软性隐形眼镜中每组选取两片镜片用于参数稳定性实验。6名受试者佩戴镜片1天。在20℃下对镜片后光学区半径、总直径、后顶点屈光力、中心厚度和含水量进行检测。在镜片佩戴前及佩戴6小时后，于35℃下对含水量、透氧性、总直径和后光学区半径进行体外测量。在镜片佩戴前后对镜片的变形、变色和镜片质量进行评估。当温度从20℃升至35℃时，观察到所有类型镜片的含水量均显著降低，并且大多数类型镜片的总直径也显著减小。在睁眼佩戴6小时后，所有类型镜片的含水量、透氧性、总直径和后光学区半径均降低。对于大多数类型的镜片，这些变化具有统计学意义。除了甲基丙烯酸羟乙酯/甲基丙烯酸70%的镜片外，在整个研究过程中镜片的变形、变色和质量均保持不变。综合本研究中产生的多个参数，得出以下结论。高含水量材料在佩戴6小时后透氧性的相对变化较小。软性隐形眼镜脱水会导致在佩戴6小时后透氧性和总直径降低。这些结果将有助于从业者预测因镜片佩戴而导致的软性隐形眼镜参数和氧气性能的变化。
