Bacterial keratitis and inflammatory corneal reactions: possible relations to contact lens oxygen transmissibility: the Harold A. Stein Lectureship 2001.
OBJECTIVE
Conventional contact lenses, particularly when used for extended wear (EW), are still associated with a high incidence of microbial keratitis and inflammatory reactions. This article discusses the possible relationship of such complications to contact lens oxygen transmissibility (Dk/t).


METHODS
The literature, including our own work, is reviewed in regard to the binding of bacteria to the corneal epithelium and receptors likely to be associated with such binding, as well as the incidence of microbial keratitis and inflammatory reactions, in relation to conventional, lower Dk/t contact lenses and new, high Dk/t soft silicone hydrogel lenses.


RESULTS
Receptors for lectins and, presumably, for bacteria such as Pseudomonas aeruginosa on the surface of the corneal epithelium are exposed in significantly higher numbers after wear of low Dk/t contact lenses than after wear of higher Dk/t lenses; and binding of P. aeruginosa follows the same pattern. Thus, it seems that high Dk/t lenses may reduce the risk of microbial keratitis. Published results of clinical trials of high Dk/t soft silicone hydrogel lenses worn for 7-day EW or 30-day continuous wear (CW), including our own 1-year study of 504 patients, are promising in so far as no cases of bacterial keratitis have yet been reported. In our study of high Dk/t silicone hydrogels, the incidence of inflammatory reactions, such as sterile infiltrates, was significantly lower than in studies of conventional soft lenses. Thus, it may be possible that inflammatory reactions also are related to oxygen transmissibility.


CONCLUSIONS
High Dk/t contact lenses seem to reduce the rate of complications.
Nilsson
Sven Erik G
SE
Department of Ophthalmology, Linköping University, Sweden. svenerik.nillsson@eye.liu
D000818:Animals; D001424:Bacterial Infections / Q000150:complications*; D003261:Contact Lenses / Q000009:adverse effects*; D003316:Corneal Diseases / Q000382:microbiology*; D006801:Humans; D007634:Keratitis / Q000382:microbiology*; D010100:Oxygen; D010539:Permeability
D010100:Oxygen