Clinical signs of hypoxia with high-Dk soft lens extended wear: is the cornea convinced?

PURPOSE: To assess the effectiveness of high-Dk soft contact lenses with oxygen transmissibility (Dk/L) beyond the critical level required to avoid corneal edema during overnight wear. METHODS: The most up-to-date data available on clinical signs of hypoxia with high-Dk contact lenses is reviewed. RESULTS: Chronic corneal edema associated with hypoxia is responsible for the development of large numbers of microcysts, limbal hyperemia, neovascularization, and small increases in myopia. Silicone hydrogel lenses worn continuously for up to 30 nights prevent corneal edema during overnight wear and do not induce a microcyst response. Long-term clinical trials indicate the mean level of limbal redness for patients wearing high-Dk lenses during continuous wear are equivalent to nonlens wearers. No changes in refractive error are associated with continuous wear of high-Dk lenses. CONCLUSION: High-Dk silicone hydrogel lenses can be worn for up to 3 years with virtual elimination of the hypoxic consequences observed with low-Dk lenses made from conventional lens materials.