Are hypoxia or modulus causes of contact lens‐associated keratitis?

Thirty years of ‘quiet eye’ with etafilcon A contact lenses

“…That microbial keratitis is not reduced with silicone hydrogel lenses and the rate of corneal infiltrative events (CIEs) is higher in reusable silicone hydrogel lens wear compared to hydrogel lens wear [99][100][101][102][103] suggests that corneal oxygenation is not a key determinant for such adverse events. Some authors have speculated that materials with a higher modulus of elasticity (which is typically greater in siliconecontaining materials) may also be implicated in the aetiology of CIEs, due to the greater mechanical impact of such lenses on the corneal surface [104,105].…”

Is it the modulus or the method that matters?

“…EDITOR: In a guest editorial entitled ‘Are hypoxia or modulus causes of contact lens‐associated keratitis?’ Efron and Morgan 1 address recent epidemiological evidence that reveals an unexpected lack of reduction in the incidence of keratitis since the advent of silicone hydrogel lenses 2,3 . They discuss the role of hypoxia in the pathogenesis of contact lens‐associated corneal infection and then go on to state that much of the keratitis reported in the Manchester Keratitis Study 4 may be attributed to various confounding factors, of which they propose the strongest candidate is lens modulus.…”

“…One needs to bear in mind that high modulus, disposable lenses and gas‐permeable contact lenses are comfortable and extremely well accepted by a majority of patients when fitted carefully. Efron and Morgan 1 concede that ‘rigid lenses, which have a very high modulus, are associated with relatively low levels of microbial keratitis’.…”