title: The Central Retinal Vein Bypass Study: a trial of laser-induced chorioretinal venous anastomosis for central retinal vein occlusion.
abstract: OBJECTIVE
  To evaluate the effectiveness of a laser-induced chorioretinal venous anastomosis (L-CRA) as a treatment for nonischemic central retinal vein occlusion (CRVO).
  
  
  METHODS
  Prospective, randomized, controlled, multicenter clinical trial.
  
  
  METHODS
  A total of 113 consecutive patients with a nonischemic CRVO of >3 months' duration and visual acuity of < or =20/50.
  
  
  METHODS
  Patients were randomized to L-CRA (58 patients) or conventional care (55 patients). They underwent standardized retinal photography, fluorescein angiography, and ophthalmic examinations, together with standardized assessments of best-corrected visual acuity, performed by masked visual acuity assessors using Early Treatment Diabetic Retinopathy Study protocols. Analysis was performed by intention-to-treat.
  
  
  METHODS
  The primary outcome measure was change in visual acuity at 18 months. Secondary outcomes were progression of retinal ischemia and rates of adverse events.
  
  
  RESULTS
  A total of 53 control patients and 55 treatment patients completed the study. The 2 groups were comparable for age, age- and gender-adjusted mean visual acuity, and most other parameters. In the treated group of 55 patients, 42 (76.4%) developed an L-CRA. Over the 18-month follow-up period, treated eyes had an 8.3 letter mean improvement from baseline compared with control eyes (P = 0.03). Treated eyes that developed a functional L-CRA achieved an 11.7 letter mean improvement from baseline over the control group after 18 months (P = 0.004). Conversion to the ischemic CRVO category occurred in 20.8% of control eyes and in 9.6% of treated eyes overall (P = 0.33). Of the treated group who developed an L-CRA where the retinal ischemia was due to progression of the CRVO, 4.9% progressed to the ischemic category (P = 0.03). Neovascularization developed at the site of the L-CRA in 10 of 55 treated eyes (18.2%). Vitrectomy surgery was required by 5 of 55 treated eyes (9.1%) because of macular traction or nonresolving vitreous hemorrhage.
  
  
  CONCLUSIONS
  Chorioretinal venous anastomosis was created in 76.4% of eyes with nonischemic CRVO in this study. Eyes that developed an anastomosis had a significant improvement (11.7 letters) in final visual acuity after 18 months, compared with eyes in the control group (P = 0.004). Complications were managed successfully with careful follow-up and early intervention.
authors.affiliation: Centre for Ophthalmology and Visual Science, Lions Eye Institute, The University of Western Australia, Perth, Australia. ianmcallister@lei.org.au
authors.forename: Ian L
authors.initials: IL
authors.lastname: McAllister
authors.forename: Mark E
authors.initials: ME
authors.lastname: Gillies
authors.forename: Lynne A
authors.initials: LA
authors.lastname: Smithies
authors.forename: Elena
authors.initials: E
authors.lastname: Rochtchina
authors.forename: Colin A
authors.initials: CA
authors.lastname: Harper
authors.forename: Mark D
authors.initials: MD
authors.lastname: Daniell
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Constable
authors.forename: Paul
authors.initials: P
authors.lastname: Mitchell
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000714:Anastomosis, Surgical; D002829:Choroid / Q000098:blood supply*; D005260:Female; D005451:Fluorescein Angiography; D005500:Follow-Up Studies; D006801:Humans; D053685:Laser Therapy; D053844:Lasers, Solid-State; D008297:Male; D008875:Middle Aged; D010781:Photography; D011446:Prospective Studies; D012169:Retinal Vein / Q000601:surgery*; D012170:Retinal Vein Occlusion / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology