title: Response of choroidal blood flow to carbogen breathing in smokers and non-smokers.
abstract: OBJECTIVE
  To investigate a potential difference in ocular vascular reactivity during carbogen breathing in optic nerve head, choroid, and retina between healthy smokers and non-smokers.
  
  
  METHODS
  25 (13 smokers and 12 non-smokers) healthy male volunteers participated in this observer masked, two cohort study. During inhalation of carbogen (5% CO(2) and 95% O(2)) over 10 minutes measurements were taken using laser Doppler flowmetry to assess submacular choroidal and optic nerve head blood flow, laser interferometry to assess fundus pulsation amplitudes, and retinal vessel analyser (RVA) to assess retinal vessel diameters.
  
  
  RESULTS
  At baseline choroidal blood flow was higher (p = 0.018, ANOVA) in smokers than in non-smokers. During administration of carbogen the response in choroidal blood flow was significantly different between the two groups: there was an increase in non-smokers after carbogen breathing (p = 0.048) compared with relatively stable blood flow in smokers (p = 0.049 between groups, ANOVA). A similar response pattern was seen for fundus pulsation amplitude, which increased notably after carbogen breathing in non-smokers but not in smokers (p<0.001 between groups, ANOVA). Optic nerve head blood flow and retinal vessel diameters were reduced in both groups to a comparable degree during carbogen breathing.
  
  
  CONCLUSIONS
  The study indicated abnormal choroidal vascular reactivity in chronic smokers. These early haemodynamic changes may be related to the increased risk to smokers of developing ocular vascular diseases. The specific mechanisms underlying abnormal choroidal vascular reactivity in chronic smokers remain to be characterised.
authors.affiliation: Department of Clinical Pharmacology, Allgemeines Krankenhaus Wien, Vienna, Austria.
authors.forename: B
authors.initials: B
authors.lastname: Wimpissinger
authors.forename: H
authors.initials: H
authors.lastname: Resch
authors.forename: F
authors.initials: F
authors.lastname: Berisha
authors.forename: G
authors.initials: G
authors.lastname: Weigert
authors.forename: L
authors.initials: L
authors.lastname: Schmetterer
authors.forename: K
authors.initials: K
authors.lastname: Polak
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002245:Carbon Dioxide / Q000008:administration & dosage*; D016022:Case-Control Studies; D002829:Choroid / Q000098:blood supply*; D005654:Fundus Oculi; D006801:Humans; D001239:Inhalation; D017078:Laser-Doppler Flowmetry; D008297:Male; D009898:Optic Disk / Q000098:blood supply / Q000187:drug effects; D010100:Oxygen / Q000008:administration & dosage*; D012039:Regional Blood Flow / Q000187:drug effects; D012171:Retinal Vessels / Q000033:anatomy & histology / Q000187:drug effects; D016037:Single-Blind Method; D012907:Smoking / Q000009:adverse effects*; D014661:Vasoconstriction
chemical_list: D002245:Carbon Dioxide; C011700:carbogen; D010100:Oxygen