Why daily wear is still better than extended wear.

Among the many problems complicating contact lens wear, microbial keratitis is of most concern because of its potential for substantial morbidity. Three decades of basic and clinical research suggest that risk factors include poor care compliance and extended wear through one or multiple sleep cycles. Many believe the latter problem is caused in part or in whole to contact lens-induced hypoxia. New contact lenses, both rigid and soft, have been developed that allow oxygen delivery equivalent to the noncontact lens state, under open-eye conditions and close to the same even for closed-eye conditions. But will such lenses reduce the risk for microbial keratitis? The authors argue that until such a conclusion is reached through clinical trials, the question remains in doubt.