title: Factors affecting the morbidity of contact lens-related microbial keratitis: a population study.
abstract: OBJECTIVE
  To examine factors influencing the severity of soft contact lens (SCL)-related microbial keratitis.
  
  
  METHODS
  Cases were detected via surveillance studies in Australia and New Zealand. Factors affecting disease severity (costs, days of symptoms, and 2 or more lines of vision loss) were examined and included age; gender; delay in SCL removal, seeking consultation, or receiving treatment; overnight wear; SCL material (hydrogel or silicone hydrogel [SiH]); and causative organism.
  
  
  RESULTS
  Two hundred ninety-seven cases were identified: 61% female, age: 35 +/- 13 years (mean +/- SD). Treatment costs were (median [interquartile range]) $760 [1859] and indirect costs were $468 [1810]. Patients were symptomatic for 7 [11] days, and vision loss occurred in 14.3% of cases. Cases with pathogenic causative organisms (66/297, 22%) were 11.4 times (95% confidence interval [CI], 4.2-30.9) more likely to result in vision loss, had longer duration of symptoms (21 [40] vs. 6 [8] days, P < 0.001) and incurred higher costs (5,512 [14,733] vs. 1,048[8,325], P < 0.001). Delays (>12 hours) before treatment increased the likelihood of vision loss (P = 0.048) disease duration (P = 0.004), and associated costs (P = 0.009). Remoteness increased the risk of vision loss (odds ratio [OR] = 5.1; 95% CI 1.6-16.6), and individuals over 28 years of age had longer disease duration (P = 0.02). In overnight wear and after adjustment for culture result and treatment delays, SiH wearers had slightly shorter disease duration (4 [4] vs. 7 [10] days, P = 0.02) but a rate of vision loss and cost similar to those of hydrogel wearers.
  
  
  CONCLUSIONS
  The causative organism was the major determinant of severity; however, modifiable factors such as delays in treatment had considerable influence. Duration of symptoms was shorter in SiH wearers, but other factors dominated disease outcome in this population study.
authors.affiliation: School of Optometry and Vision Science University of New South Wales, Sydney NSW, Australia. l.keay@ier.org.au
authors.forename: Lisa
authors.initials: L
authors.lastname: Keay
authors.forename: Katie
authors.initials: K
authors.lastname: Edwards
authors.forename: Thomas
authors.initials: T
authors.lastname: Naduvilath
authors.forename: Kevin
authors.initials: K
authors.lastname: Forde
authors.forename: Fiona
authors.initials: F
authors.lastname: Stapleton
mesh_terms: D000293:Adolescent; D000328:Adult; D001315:Australia / Q000453:epidemiology; D003263:Contact Lenses, Hydrophilic / Q000009:adverse effects*; D003320:Corneal Ulcer / Q000191:economics / Q000453:epidemiology* / Q000382:microbiology; D015817:Eye Infections / Q000191:economics / Q000453:epidemiology* / Q000382:microbiology; D005260:Female; D017048:Health Care Costs; D017721:Hospital Costs; D006801:Humans; D008297:Male; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D012307:Risk Factors; D014792:Visual Acuity