title: A re-evaluation of the risk of microbial keratitis from overnight contact lens wear compared with other life risks.
abstract: OBJECTIVE
  In 1995, Myers and Weiss published an article comparing the risk of ulcerative keratitis related to low oxygen permeability (Dk) extended contact lens wear to other life risks. This article updates the risks associated with silicone hydrogel (SH) extended wear contact lens use and some comparative life risks, to provide a current perspective within the hierarchy of life risks.
  
  
  METHODS
  A comparative ratio was defined as the incidence of microbial keratitis in a population of SH extended wear contact lens users divided by the incidence of other disease or occurrence in a given population at risk.
  
  
  RESULTS
  The risk of SH lens-related microbial keratitis is about 1.5 to 16 times less risky than certain nonfatal disruptive occurrences in the general population, and about the same as the risk of developing breast cancer. Compared with other ocular conditions, the risk of microbial keratitis with SH lenses is about the same as developing late-stage age-related macular degeneration or retinal detachment after cataract extraction on an annual basis; it is over 200 times greater than developing eye or orbit cancer; it is about 7, 20, or more than 30 times less than proceeding to penetrating keratoplasty in keratoconus, developing nuclear cataract, or experiencing a corneal inflammatory event during low-Dk extended wear, respectively.
  
  
  CONCLUSIONS
  Although the risk of microbial keratitis with modern day SH contact lens extended wear has not changed since the 1980s, when put in perspective with other life risks, it is a relatively rare occurrence.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA. loretta.szczotka@uhhospitals.org
authors.forename: Loretta
authors.initials: L
authors.lastname: Szczotka-Flynn
authors.forename: Rouzbeh
authors.initials: R
authors.lastname: Ahmadian
authors.forename: Mireya
authors.initials: M
authors.lastname: Diaz
mesh_terms: D002940:Circadian Rhythm; D003262:Contact Lenses, Extended-Wear / Q000009:adverse effects*; D015817:Eye Infections / Q000209:etiology*; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D015994:Incidence; D007634:Keratitis / Q000453:epidemiology / Q000382:microbiology*; D018570:Risk Assessment; D012828:Silicones
chemical_list: D012828:Silicones; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate