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C.F. Radford, F. Stapleton, S. Verma, D.C. Minassian, J.K. G. Dart; Microbial Keratitis Among Users of Silicone Hydrogel Contact Lenses: Interim Analysis of a Case Control Study . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5564.
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© ARVO (1962-2015); The Authors (2016-present)
To assess risk factors for contact lens (CL) related microbial keratitis (MK) among users of silicone hydrogel (SH) lenses.
A 2 year case–control study commenced in December 2003. Cases were CL wearers attending as new patients to Moorfields Eye Hospital (MEH) Accident and Emergency (A&E) with proven or presumed MK. There were two groups of controls: Hospital Controls (H–Cs) were CL wearers attending A&E as new patients with a disorder unrelated to CL wear, and Population–based Controls (POP–Cs) were CL wearers randomly selected from the MEH A&E catchment area who had never attended MEH. Persons with a medical indication for CL wear were excluded. Hospital patients completed a self–administered questionnaire, while POP–Cs were interviewed by telephone. Interim results for the SH CL users are presented.
After 22 months there were 50 cases who had been using SH CL, including 9 (18%) with a positive culture of Pseudomonas (n=5) or other bacteria (n=4). Among the 9 patients with central lesions, 6 achieved a final acuity of 6/6 or more. There were 70 H–Cs and 34 POP–Cs wearing SH CL. Multiple logistic regression analysis of the data was initially carried out using H–Cs and POP–Cs separately, but since the main findings were similar, analysis was repeated with controls combined. The only significant risk factor in this interim analysis was overnight wear. When compared to the 52 (34%) people using the lenses on a strictly daily wear basis, those sleeping in the lenses overnight up to 25 times per month had a 7 times increased risk of MK (odds ratio (OR): 6.64, 95% confidence limits (cl) 1.31–33.64, p=0.022), while those with 26–31 nights per month of overnight use had a 14 times greater risk (OR: 14.34, 95% cl 2.58–79.60, p=0.002).
This interim analysis suggests that, even among users of lenses with high oxygen transmissibility, overnight wear continues to be a major risk factor for CL related MK.
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