title: Vitrectomy surgery increases oxygen exposure to the lens: a possible mechanism for nuclear cataract formation.
abstract: OBJECTIVE
  To report vitreous oxygen tension before, immediately after, and at longer times after vitrectomy.
  
  
  METHODS
  A prospective, interventional consecutive case series.
  
  
  METHODS
  Oxygen was measured using an optical oxygen sensor in patients undergoing vitrectomy. Intraoperatively, oxygen measurements were taken before and after vitrectomy in two intraocular locations: adjacent to the lens and in the mid-vitreous.
  
  
  RESULTS
  Sixty-nine eyes underwent oxygen tension measurements at the time of vitrectomy. In baseline eyes, oxygen tension in the vitreous was low, measuring 8.7 +/- 0.6 mm Hg adjacent to the lens and 7.1 +/- 0.5 mm Hg in the mid-vitreous. The difference between the two locations was statistically significant (P < .003), indicating that vitreous gel maintains an intraocular oxygen gradient. Immediately after vitrectomy, oxygen tension in the fluid-filled eye was higher, measuring 69.6 +/-4.8 mm Hg adjacent to the lens and 75.6 +/- 4.1 mm Hg in the mid-vitreous. There was no statistically significant oxygen gradient between the two locations. The difference in oxygen tension pre- and postvitrectomy is highly statistically significant (P < .0001 lens, P < .0001 mid-vitreous). In eyes with a history of vitrectomy and previous removal of the vitreous gel, the intraocular oxygen tension was significantly higher than in eyes with a formed vitreous gel undergoing a first vitrectomy (P < .02 lens, P < .003 mid-vitreous).
  
  
  CONCLUSIONS
  Vitrectomy surgery significantly increases intraocular oxygen tension during and for prolonged periods after surgery. This exposes the crystalline lens to abnormally high oxygen and may lead to nuclear cataract formation.
authors.affiliation: Barnes Retina Institute, St. Louis, Missouri, 63144, USA. nholekamp@pol.net
authors.forename: Nancy M
authors.initials: NM
authors.lastname: Holekamp
authors.forename: Ying-Bo
authors.initials: YB
authors.lastname: Shui
authors.forename: David C
authors.initials: DC
authors.lastname: Beebe
mesh_terms: D000368:Aged; D002386:Cataract / Q000209:etiology / Q000378:metabolism*; D005260:Female; D006801:Humans; D017736:Ion-Selective Electrodes; D007907:Lens Nucleus, Crystalline / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000009:adverse effects / Q000378:metabolism*; D011446:Prospective Studies; D012164:Retinal Diseases / Q000601:surgery; D014821:Vitrectomy; D014822:Vitreous Body / Q000378:metabolism*
chemical_list: D010100:Oxygen