Benjamin W J
University of Alabama at Birmingham School of Optometry 35294.
J Am Optom Assoc. 1994 Mar;65(3):169-72.
INTRODUCTION. Oxygen permeability (Dk) of available hydrogel materials used for soft contact lenses is currently restricted by the oxygen permeability of water at 80 Dk units. A predicted upper limit for conventional hydrogels amenable for use as a contact lens, has been 37 Dk units obtained with a water content of 80%. Methods for increasing oxygen permeability beyond that determined by water content must be explored, in order to further advance the physiological compatibility of hydrogel contact lenses.
Oxygen transport characteristics of a prototype nonconventional hydrogel contact lens material were derived in terms of human equivalent oxygen percentage (EOP) and thickness (L). The oxygen permeability of the material and oxygen transmissibilities (Dk/L) of various thicknesses were computed on the bases of a recently published nonlinear EOP vs. Dk/L relationship.
The material's oxygen permeability (Dk) was determined to be approximately 35 Dk units compared to 12.7 Dk units calculated for a conventional gel material having the same water content (52% H2O). Oxygen permeability equivalent to that obtained with high-water conventional gels was achieved using this mid-water nonconventional hydrogel. The prototype material was apparently also capable of low critical thicknesses typical of low-water conventional gels.
Should new gel materials be durable with critical thicknesses in the "ultra-thin" range, nonconventional gel lenses could be capable of super and perhaps even hyper transmissibility with central minus lens EOP between 15-18.5% and Dk/L between 50-90 Dk/L units. The conventional relationships between water content and oxygen transmissibility of hydrogel contact lenses appear to have been surpassed. However, significant additional hurdles have yet to be overcome before nonconventional hydrogel materials can be ready for the ophthalmic marketplace.
引言。目前，用于软性隐形眼镜的现有水凝胶材料的透氧性（Dk）受水的透氧性限制，为80 Dk单位。适用于隐形眼镜的传统水凝胶的预测上限为37 Dk单位，含水量为80%。必须探索提高透氧性超过由含水量决定的水平的方法，以进一步提升水凝胶隐形眼镜的生理相容性。
根据人体等效氧百分比（EOP）和厚度（L）推导了一种原型非传统水凝胶隐形眼镜材料的氧传输特性。基于最近发表的非线性EOP与Dk/L关系，计算了该材料的透氧性以及不同厚度的氧透过率（Dk/L）。
该材料的透氧性（Dk）测定约为35 Dk单位，而具有相同含水量（52% H₂O）的传统凝胶材料计算得出的透氧性为12.7 Dk单位。使用这种中等含水量的非传统水凝胶实现了与高含水量传统凝胶相当的透氧性。该原型材料显然还能够达到低含水量传统凝胶典型的低临界厚度。
如果新的凝胶材料在“超薄”范围内具有临界厚度且耐用，非传统凝胶隐形眼镜可能具有超高甚至极高的透过率，中央负透镜EOP在15 - 18.5%之间，Dk/L在50 - 90 Dk/L单位之间。水凝胶隐形眼镜含水量与氧透过率之间的传统关系似乎已被超越。然而，在非传统水凝胶材料能够进入眼科市场之前，还有重大的额外障碍有待克服。
