氧气与角膜接触镜配戴

全球大约有八千万人 (约占总人口的 1.5 % )在配戴角膜接触镜 ,镜片的透氧性及配戴角膜接触镜后角膜的获氧状态是保证配戴安全性和有效性的关键。角膜需要多种营养物质以保证其正常的代谢功能 ,氧气是其中是重要的部分 ,只有在充分氧供的状态下 ,角膜才能保持稳定的 78%的水合状态 ,保证角膜透明性。为了进一步了解氧气与角膜接触镜配戴的关系 ,本文着重对角膜接触镜所致的角膜缺氧的主要表现及角膜接触镜的透氧性能及其表达指标作一综述。配戴角膜接触镜后 ,角膜的氧供明显减少 ,特别在闭眼状态下氧供减少尤其明显 ,角膜接触镜引起的角膜缺氧变化主要表现为 :①角膜上皮 :角膜上皮水肿 ,即因细胞间隙中水液充盈而发生的微囊样水肿 ,水肿明显时会影响视力并使角膜的敏感性下降 ;②角膜基质 :角膜基质水肿达 5 %以上即可从裂隙灯检查中发现 ,主要表现为条纹或皱褶 ,长期慢性水肿会诱发角膜新生血管的发生 ,逐步发生角膜疤痕、屈光改变等一系列问题 ;③角膜内皮 :慢性角膜缺氧最终会导致角膜内皮细胞形态的改变 ,而且无法代偿。保持角膜功能的最低需氧量称为“临界氧” ,理想的角膜接触镜应该是通过该镜片后到达角膜面的氧供超过临界氧。角膜接触镜的透氧性能表达指标主要有 :透氧性 (oxygenpermeability

Oxygen and Contact Lens Wear

In this article we review the role of oxygen and contact lens wear related to the metabolic processes of the cornea.The critical oxygen requirement of the cornea for maintenance of its normal hydration level to ensure transparency is discussed,as well as the subsequent reversible and irreversible changes to the corneal layers if this requirement is not met.We review the concept of oxygen transmission and its application to rigid gas permeable and soft contact lens material.Corneal responses to induced hypoxia related to extended wear of contact lenses as well as other complications,such as infection,are discussed.In conclusion,we comment on the oxygen performance of a new generation of silicone hydrogel contact lens materials and the future of extended wear.