Brennan N A, Efron N, Carney L G
Department of Optometry, University of Melbourne, Parkville, Australia.
Am J Optom Physiol Opt. 1988 Jan;65(1):19-24. doi: 10.1097/00006324-198801000-00004.
Three distinct methodologies have been used to assess corneal oxygen supply during contact lens wear--oxygen transmissibility (Dk/L), equivalent oxygen percentage (EOP), and corneal swelling. To examine the interelation among these methodologies, we measured the EOP and the amount of corneal swelling in response to a set of contact lenses of a range of Dk/L values on 10 subjects. We also measured the corneal swelling response after exposure to gas mixtures of 0.00, 1.01, 2.65, 5.13, and 10.3% oxygen concentration (balance nitrogen). Analysis of covariance showed that the relation between corneal swelling and EOP during lens wear was significantly different from the relation between corneal swelling and oxygen concentration after exposure to the gas mixtures, leading to different estimates of the minimum oxygen tension required to avoid corneal swelling (18.0% for the EOP technique vs. 10.9% for the gas mixtures). This discrepancy may be explained in terms of the underlying assumptions of the various techniques and by consideration of the mechanisms of corneal swelling during contact lens wear. The clinical implication of this result is that an EOP of 18% should be used as the basis for the development of a daily wear contact lens that provides an "edemafree" response.
在佩戴隐形眼镜期间，已采用三种不同的方法来评估角膜的氧气供应——氧气透过率（Dk/L）、等效氧百分比（EOP）和角膜肿胀情况。为了研究这些方法之间的相互关系，我们对10名受试者佩戴了一系列具有不同Dk/L值的隐形眼镜，并测量了其EOP和角膜肿胀量。我们还测量了在暴露于氧气浓度分别为0.00%、1.01%、2.65%、5.13%和10.3%（其余为氮气）的混合气体后角膜的肿胀反应。协方差分析表明，佩戴隐形眼镜期间角膜肿胀与EOP之间的关系与暴露于混合气体后角膜肿胀与氧气浓度之间的关系显著不同，这导致了对避免角膜肿胀所需的最低氧张力的不同估计（EOP技术为18.0%，混合气体为10.9%）。这种差异可以根据各种技术的潜在假设以及考虑隐形眼镜佩戴期间角膜肿胀的机制来解释。该结果的临床意义在于，应将18%的EOP作为开发能提供“无水肿”反应的日戴型隐形眼镜的依据。
