Characteristics of and risk factors for contact lens-related microbial keratitis in a tertiary referral hospital

Aim A retrospective case-control study was conducted at a tertiary referral hospital to determine the characteristics of and risk factors for contact lens ( CL) related presumed microbial keratitis. Methods Two hundred and ninety-one cases of presumed microbial keratitis were retrospectively identified over a 2-year period. Records were reviewed for a history of CL wear and, where identified, CL, demographic, and clinical data were collected. Lens wearing controls (n = 186) were identified by a community telephone survey. Multiple logistic regression estimated risk factors for infection and vision loss. Results Ninety-nine (34%) new cases of presumed microbial keratitis were associated with CL wear. Overnight soft CL use was associated with an increased risk of infection compared to daily disposable CL wear ( odds ratio ( OR): 8.03, 95% confidence interval (CI): 1.82-35.46). Compared with older CL wearers, 15-24 year olds had a 3.5 times greater risk of infection ( OR, 95% CI: 1.7-7.4). Of the 84 cases with available data, 24 (29%) lost two or more lines of best-corrected visual acuity. Delaying treatment by 49-72 h had a 4.5 times ( OR, 95% CI: 1.4-14.9) greater risk of visual loss compared to seeking treatment early. Of the 99 cases of infection, 88 were scraped and 78% (69/88) of these returned a positive culture. Gram-positive bacteria were the predominant causative organisms. Conclusion Overnight use of CL and youth carry a greater risk of infection. Practitioners should reinforce the importance of proper CL care at all times, and early presentation following the onset of symptoms.