Microbial keratitis (MK) is the most visually devastating complication associated
with contact lens wear. Pseudomonas aeruginosa (PA) is highly
invasive in the corneal epithelium and is responsible for more than half of the
reported cases of contact lens-related MK. To protect against
Pseudomonas-mediated MK, the corneal epithelium has evolved
overlapping defense mechanisms that function to protect the ocular surface from
microbial invasion. Research has shown that contact lens wear disrupts these
protective mechanisms through breakdown of normal homeostatic surface renewal as
well as damaging the corneal surface, exposing underlying cell membrane
receptors that bind and internalize PA through the formation of lipid rafts.
Human clinical trials have shown that initial adherence of PA with resulting
increased risk for microbial infection is mediated in part by contact lens
oxygen transmissibility. Recently, chemical preserved multipurpose solutions
(MPS) have been implicated in increasing PA adherence to corneal epithelial
cells, in addition to inducing significant levels of toxic staining when used in
conjunction with specific silicone hydrogel lenses. This review summarizes what
is currently known about the relationship between contact lenses, the corneal
epithelium, MPS, and infection
