Purpose: This article reviews the corneal changes resulting from the hypoxia that occurs during sleep and specifically during contact lens wear.
Methods: Discussion includes a literature review and observations regarding the changes to the corneal epithelium, stroma, and endothelium that take place during sleep and wearing of contact lenses made from different materials.
Results: Hypoxia and hypercapnia cause significant changes to the corneal epithelium, stroma, and endothelium. Some of these changes can also be seen following the sleep cycle. Epithelial changes include decreased metabolic rate, morphologic changes, microcysts, changes in junctional integrity, decreased corneal sensation, and pannus formation. Stromal changes include stromal edema, stromal acidosis, neovascularization, and changes in corneal shape and, ultimately, corneal thinning. Endothelial changes include bleb formation, polymegethism, changes in endothelial cell density, and possible changes in endothelial function.
Conclusions: There are multiple and significant corneal changes resulting from hypoxia and hypercapnia. These changes vary with the specific lens style. The high-oxygen-permeable contact lenses recently introduced may overcome some of these problems.