title: Pars plana vitrectomy in the Early Treatment Diabetic Retinopathy Study. ETDRS report number 17. The Early Treatment Diabetic Retinopathy Study Research Group.
abstract: BACKGROUND
  The Early Treatment Diabetic Retinopathy Study (ETDRS) enrolled 3711 patients with mild-to-severe nonproliferative or early proliferative diabetic retinopathy in both eyes. Patients were randomly assigned to aspirin 650 mg/day or placebo. One eye of each patient was assigned randomly to early photocoagulation and the other to deferral of photocoagulation. Follow-up examinations were scheduled at least every 4 months, and photocoagulation was initiated in eyes assigned to deferral as soon as high-risk proliferative retinopathy was detected. Aspirin was not found to have an effect on retinopathy progression or rates of vitreous hemorrhage. The risk of a combined end point, severe visual loss or vitrectomy, was low in eyes assigned to deferral (6% at 5 years) and was reduced by early photocoagulation (4% at 5 years). Vitrectomy was carried out in 208 patients during the 9 years of the study. This report presents baseline and previtrectomy characteristics and visual outcome in these patients.
  
  
  METHODS
  Information collected at baseline and during follow-up as part of the ETDRS protocol was supplemented by review of clinic charts for visual acuity and ocular status immediately before vitrectomy.
  
  
  RESULTS
  Vitrectomy was performed in 208 (5.6%) of the 3711 patients (243 eyes) enrolled in the ETDRS. The 5-year vitrectomy rates for eyes grouped by their initial photocoagulation assignment were as follows: 2.1% in the early full scatter photocoagulation group, 2.5% in the early mild scatter group, and 4.0% in the deferral group. The 5-year rates of vitrectomy (in one or both eyes) were 5.4% in patients assigned to aspirin and 5.2% in patients assigned to a placebo. The indications for vitrectomy were either vitreous hemorrhage (53.9%) or retinal detachment with or without vitreous hemorrhage (46.1%). Before vitrectomy, visual acuity was 5/200 or worse in 66.7% of eyes and better than 20/100 in 6.2%. One year after vitrectomy, the visual acuity was 20/100 or better in 47.6% of eyes, including 24.0% with visual acuity of 20/40 or better.
  
  
  CONCLUSIONS
  With frequent follow-up examinations and timely scatter (panretinal) photocoagulation, the 5-year cumulative rate of pars plana vitrectomy in ETDRS patients was 5.3%. Aspirin use did not influence the rate of vitrectomy.
authors.affiliation: Department of Ophtalmology, Bascom Palmer Eye Institute, University of Miami School of Medicine.
authors.forename: H W
authors.initials: HW
authors.lastname: Flynn
authors.forename: E Y
authors.initials: EY
authors.lastname: Chew
authors.forename: B D
authors.initials: BD
authors.lastname: Simons
authors.forename: F B
authors.initials: FB
authors.lastname: Barton
authors.forename: N A
authors.initials: NA
authors.lastname: Remaley
authors.forename: F L
authors.initials: FL
authors.lastname: Ferris
mesh_terms: D000328:Adult; D001241:Aspirin / Q000627:therapeutic use; D003930:Diabetic Retinopathy / Q000188:drug therapy / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D017075:Laser Coagulation; D008297:Male; D008875:Middle Aged; D012163:Retinal Detachment / Q000601:surgery; D016896:Treatment Outcome; D014792:Visual Acuity; D014821:Vitrectomy; D014823:Vitreous Hemorrhage / Q000601:surgery
chemical_list: D001241:Aspirin