title: Cigarette smoking is negatively associated with keratoconus.
abstract: OBJECTIVE
  To investigate a correlation between cigarette smoking and keratoconus.
  
  
  METHODS
  Patients with keratoconus who were treated with corneal collagen cross-linking from June 2006 to November 2007 were asked about their smoking habits. A person smoking a minimum of two cigarettes per day for more than 1 year was classified as a smoker.
  
  
  RESULTS
  A total of 180 patients with keratoconus (mean age 28 +/- 9 years [range: 15 to 41 years]) were asked about their smoking habits. One hundred seventy-one (95%) were non-smokers and only 9 (5%) were smokers (95% confidence interval, 2.31 to 9.28). Using the chi-square test, a significant correlation was found between non-smokers and keratoconus (P < .001).
  
  
  CONCLUSIONS
  In this group of patients with keratoconus, few were smokers. Cigarette smoke contains toxic substances. Consequently, people are advised not to smoke. However, we speculate that the by-products of cigarette smoke may lead to cross-linking of collagen, which in the cornea, may prevent the development and progression of keratoconus.
authors.affiliation: Department of Ophthalmology, Technical University Dresden, Germany. eberhard.spoerl@uniklinikum-dresden.de
authors.forename: Eberhard
authors.initials: E
authors.lastname: Spoerl
authors.forename: Frederik
authors.initials: F
authors.lastname: Raiskup-Wolf
authors.forename: Eberhard
authors.initials: E
authors.lastname: Kuhlisch
authors.forename: Lutz E
authors.initials: LE
authors.lastname: Pillunat
mesh_terms: D000293:Adolescent; D000328:Adult; D003094:Collagen / Q000378:metabolism; D003319:Corneal Stroma / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D018450:Disease Progression; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000188:drug therapy / Q000209:etiology* / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use; D012256:Riboflavin / Q000627:therapeutic use; D012907:Smoking / Q000009:adverse effects* / Q000523:psychology; D011795:Surveys and Questionnaires; D014466:Ultraviolet Rays
chemical_list: D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin