title: Does the level of available oxygen impact comfort in contact lens wear?: A review of the literature.
abstract: OBJECTIVE
  Wear of low-Dk/t lenses has long been associated with signs and symptoms indicative of hypoxia and with patient symptoms of dryness and discomfort. Although patient discomfort during soft contact lens wear has been generally attributed to lens dehydration, research studies aimed at verifying that connection have been unsuccessful. With the advent of high-Dk/t silicone hydrogel lenses, not only have improvements in clinical signs of hypoxia been documented, but improvements in patient symptoms of dryness and discomfort also have been documented. This literature review was undertaken to examine historic and current literature to determine whether the level of available oxygen is associated with patient symptoms of dryness and discomfort.
  
  
  METHODS
  Literature was reviewed related to soft contact lens dehydration, corneal hypoxia, patient symptoms of dryness and discomfort, and current clinical studies of silicone hydrogel lens wear.
  
  
  RESULTS
  Through the years, the body of knowledge has grown supporting a connection between decreased levels of available oxygen to the cornea caused by low-Dk/t contact lens wear and negative impacts on the signs of corneal health and patient symptoms.
  
  
  CONCLUSIONS
  Available published literature suggests that many of these changes in patient signs and symptoms seen with low-Dk/t lens wear may be related to an inflammatory response. Clinical studies of high-Dk/t silicone hydrogel lenses further support a significant connection between the level of available oxygen during contact lens wear and improved patient symptoms of comfort, including dryness.
authors.affiliation: CIBA Vision Corporation, Duluth, GA 30097, USA. sally.dillehay@cibavision.com
authors.forename: Sally M
authors.initials: SM
authors.lastname: Dillehay
mesh_terms: D003261:Contact Lenses / Q000009:adverse effects* / Q000266:history; D003263:Contact Lenses, Hydrophilic / Q000009:adverse effects; D003316:Corneal Diseases / Q000503:physiopathology; D003890:Desiccation; D015352:Dry Eye Syndromes / Q000209:etiology* / Q000503:physiopathology; D004777:Environment; D049673:History, 20th Century; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D007634:Keratitis / Q000503:physiopathology; D010100:Oxygen; D010146:Pain / Q000503:physiopathology
chemical_list: D010100:Oxygen