Hyperosmotic tear stimulates human corneal nerve endings, activates ocular immune response, and elicits dry-eye symptoms. A soft contact lens (SCL) covers the cornea preventing it from experiencing direct tear evaporation and the resulting blink-periodic salinity increases. For the cornea to experience hyperosmolarity due to tear evaporation, salt must transport across the SCL to the post-lens tear film (PoLTF) bathing the cornea. Consequently, limited salt transport across a SCL potentially protects the ocular surface from hyperosmotic tear. In addition, despite lens-wear discomfort sharing common sensations to dry eye, no correlation is available between measured tear hyperosmolarity and SCL-wear discomfort. Lack of documentation is likely because clinical measurements of tear osmolarity during lens wear do not interrogate the tear osmolarity of the PoLTF that actually overlays the cornea. Rather, tear osmolarity is clinically measured in the tear meniscus. For the first time, we mathematically quantify tear osmolarity in the PoLTF and show that it differs significantly from the clinically measured tear-meniscus osmolarity. We show further that aqueous-deficient dry eye and evaporative dry eye both exacerbate the hyperosmolarity of the PoLTF. Nevertheless, depending on lens salt-transport properties (i.e., diffusivity, partition coefficient, and thickness), a SCL can indeed protect against corneal hyperosmolarity by reducing PoLTF salinity to below that of the ocular surface during no-lens wear. Importantly, PoLTF osmolarity for dry-eye patients can be reduced to that of normal eyes with no-lens wear provided that the lens exhibits a low lens-salt diffusivity. Infrequent blinking increases PoLTF osmolarity consistent with lens-wear discomfort. Judicious design of SCL material salt-transport properties can ameliorate corneal hyperosmolarity. Our results confirm the importance of PoLTF osmolarity during SCL wear and indicate a possible relation between PoLTF osmolarity and contact-lens discomfort.

高渗性泪液刺激人角膜神经末梢，激活眼部免疫反应，引发干眼症。软性隐形眼镜 (SCL) 覆盖角膜，防止其经历直接泪液蒸发和由此产生的眨眼周期性盐度增加。为了使角膜因泪液蒸发而出现高渗，盐必须穿过 SCL 输送到沐浴角膜的镜片后泪膜 (PoLTF)。因此，通过 SCL 的有限盐分运输可能会保护眼表免受高渗性撕裂。此外，尽管佩戴镜片的不适感与干眼症有共同的感觉，但在测量的泪液高渗性和 SCL 佩戴不适感之间没有相关性。缺乏文件可能是因为在镜片佩戴期间泪液渗透压的临床测量并未询问实际覆盖角膜的 PoLTF 的泪液渗透压。相反，泪液渗透压是在泪液半月板临床上测量的。我们第一次在数学上量化了 PoLTF 中的泪液渗透压，并表明它与临床测量的泪液-半月板渗透压显着不同。我们进一步表明，缺水性干眼和蒸发过强型干眼都会加剧 PoLTF 的高渗性。然而，根据镜片的盐分传输特性（即扩散性、分配系数和厚度），SCL 确实可以通过在不戴镜片时将 PoLTF 盐度降低至低于眼表的盐度来防止角膜高渗。重要的，干眼患者的 PoLTF 渗透压可以降低到不戴镜片的正常眼睛，前提是镜片表现出低的镜片盐扩散率。不经常眨眼会增加 PoLTF 渗透压，这与佩戴镜片的不适感一致。SCL 材料的盐转运特性的明智设计可以改善角膜高渗性。我们的结果证实了 PoLTF 渗透压在 SCL 佩戴期间的重要性，并表明 PoLTF 渗透压和隐形眼镜不适之间可能存在关系。