title: Duration of vitrectomy and postoperative cataract in the vitrectomy for macular hole study.
abstract: OBJECTIVE
  To report the association between duration of vitrectomy, as well as other risk factors, and the progression of nuclear sclerosis and posterior subcapsular cataract in the Vitrectomy for Macular Hole Study.
  
  
  METHODS
  A cohort study nested within a randomized controlled clinical trial.
  
  
  METHODS
  Using a system similar to the Lens Opacities Classification System II, nuclear sclerosis (NS) and posterior subcapsular cataract (PSC) were scored in the vitrectomy and fellow eye of 74 patients at baseline and at 6, 12, and 24 months postoperatively. Age, baseline blood pressure and refractive power, and duration of surgery were evaluated as risk factors for NS or PSC progression and cataract extraction.
  
  
  RESULTS
  The incidence of NS progression in the surgical group of vitrectomy eyes was 81% at 6 months, 98% at 1 year, and 100% at 2 years of follow-up. In contrast, NS progression in the control group of fellow eyes was only 18% at 6 months, 20% at 1 year, and 8% at 2 years. The incidence of PSC progression in the surgical group remained at approximately 11% throughout follow-up, which was not significantly higher than the 3% to 5% incidence in the control group. Vitrectomy was significantly related to progression of NS cataract (P <.001) and cataract extraction (P <.01). No statistically significant differences were found for NS scores, PSC scores, or progression rates between eyes that had less than median surgical duration (60 min.) or more than the median surgical duration. Additionally, no significant differences were found when eyes that experienced 45 minutes or less surgical duration were compared with eyes that endured more than 75 minutes surgical duration. Age, blood pressure, and refractive power were not found to be predictors for NS and PSC progression.
  
  
  CONCLUSIONS
  Although vitrectomy is a risk factor for NS progression, the duration of vitrectomy does not increase the risk.
authors.affiliation: Department of Ophthalmology, Shiley Eye Center, University of California San Diego, 9415 Campus Point Drive, La Jolla, CA 92093-0946, USA.
authors.forename: L
authors.initials: L
authors.lastname: Cheng
authors.forename: S P
authors.initials: SP
authors.lastname: Azen
authors.forename: M H
authors.initials: MH
authors.lastname: El-Bradey
authors.forename: B M
authors.initials: BM
authors.lastname: Scholz
authors.forename: S
authors.initials: S
authors.lastname: Chaidhawangul
authors.forename: M
authors.initials: M
authors.lastname: Toyoguchi
authors.forename: W R
authors.initials: WR
authors.lastname: Freeman
mesh_terms: D000367:Age Factors; D000368:Aged; D001794:Blood Pressure; D002386:Cataract / Q000145:classification / Q000209:etiology*; D015331:Cohort Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D015994:Incidence; D007908:Lens, Crystalline / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D012029:Refraction, Ocular; D012167:Retinal Perforations / Q000601:surgery*; D012307:Risk Factors; D012598:Sclerosis; D013997:Time Factors; D014821:Vitrectomy