Mixed infection (Pseudomonas and coagulase negative staphylococci) microbial keratitis associated with extended wear silicone hydrogel contact lens

Contact lens induced ulcerative keratitis is a serious complication which can be devastating for the patient if treatment is delayed. Extended wear is the commonest cause of microbial keratitis in contact lens wear. New extended wear silicone hydrogel contact lenses have higher oxygen transmissibility so that they can be worn continuously for 30 days. They can also be used as bandage contact lenses. The risk of Pseudomonas microbial keratitis with overnight wear is significantly increased by contact lenses with low oxygen transmissibility. By virtue of high oxygen transmissibility, the silicone hydrogel contact lenses are thought to be associated with low risk of infectious keratitis. 4 So far only four cases of microbial keratitis have been reported with their use. In spite of various claims of protection against serious microbial keratitis with pathogens such as P aeruginosa, we have recently come across the first case of Pseudomonas keratitis in a patient wearing silicone hydrogel contact lenses.