Contact lens - related microbial keratitis (CLRMK)

Contact lens-related microbial keratitis (CLRMK)

• infection and inflammation of the cornea associated with microbial contamination of lenses (1,2)
• most important risk factors
  • soft contact lens wear
    • overnight wearing
    • daily wear lenses - not to be worn while sleeping
    • higher incidence of keratitis in wearers who sleep in contact lenses (3)
    • to sleep in lenses
      • silicone hydrogel lenses, carries a five times decreased risk of keratitis compared with hydrogel lenses (3)
  • extended wear
    • greater risk of corneal infection

Common organisms:

• bacterial
  • Pseudomonas aeruginosa (commonest). Klebsiella pneumoniae may also cause microbial keratitis
  • identified by occurrence of a larger infiltrate (4)
    • produces proteases
      • invade
      • destroy corneal cells
    • excessive activation of the host defense system
      • involving receptors on the corneal epithelial cells called toll-like receptors (TLRs)
      • leads to destruction of corneal cells
        • scarring and vision loss
• amoebic
  • Acanthamoeba
    • Acanthamoeba keratitis (5)
    • identified by observing a ring infiltrate
      • major risk factors
        • failure to disinfect daily wear soft contact lenses
        • use of chlorine release lens disinfection systems (little protective effect against the organism)
          • ineffective at killing Acanthamoeba cysts and trophozoites
        • improvement of contact lens disinfecting systems is needed to prevent Acanthamoeba keratitis (6)
• fungal
  • caused by fusarium (commonest) Candida , Curvularia, and Aspergillus
  • a serious corneal infection
  • associated with poor contact lens solutions (7)
    • contact lenses are a major risk factor
    • needs aggressive topical antifungal therapy
• some are Polymicrobial

Management of contact lens-associated corneal infiltrative events (CIEs) (8)

• lens wear should be suspended
• contact lens solutions discontinued
• anti-microbial therapy initiated immediately
• changes in contact lens wearing schedules, and materials
• referred to ophthalmologist immediately

Reference:

1. Preechawatmd P. Contact lens-related microbial keratitis. J Med Assoc Thai. 2007 Apr;90(4):737-43
2. Willcox MD.Pseudomonas aeruginosa infection and inflammation during contact lens wear: a review. Optom Vis Sci. 2007 Apr;84(4):273-8
3. Morgan PB et al. Incidence of keratitis of varying severity among contact lens wearers. Br J Ophthalmol. 2005 Apr;89(4):430-6
4. Dahlgren MA et al. The clinical diagnosis of microbial keratitis.Am J Ophthalmol. 2007 Jun;143(6):940-944
5. Radford CF et al. Risk factors for acanthamoeba keratitis in contact lens users: a case-control study. BMJ. 1995 Jun 17;310(6994):1567-70.
6. Tzanetou K et al. Acanthamoeba keratitis and contact lens disinfecting solutions. Ophthalmologica. 2006;220(4):238-41.
7. Chang DC et al. Multistate outbreak of Fusarium keratitis associated with use of a contact lens solution. JAMA. 2006 Aug 23;296(8):953-63
8. Efron N, Morgan PB. Rethinking contact lens associated keratitis. Clin Exp Optom. 2006 Sep;89(5):280-98
9. Suchecki JK et al. Contact lens complications.Ophthalmol Clin North Am. 2003 Sep;16(3):471-84.