title: Natural history of branch retinal vein occlusion: an evidence-based systematic review.
abstract: OBJECTIVE
  To describe the natural history of branch retinal vein occlusion (BRVO) based on the best available evidence from the literature.
  
  
  CONCLUSIONS
  Branch retinal vein occlusion is the second most frequent major retinal vascular disease. Although several new treatments for BRVO are currently being introduced, data on its natural history are sparse.
  
  
  METHODS
  English language articles were retrieved using a keyword search of MEDLINE, EMBASE, Current Contents, and the Cochrane Library to November 13, 2008, supplemented by manually searching the references of review articles published within the last 5 years. All relevant observational studies evaluating the natural history of BRVO and all clinical trials evaluating BRVO interventions with an untreated control arm were independently identified by 2 investigators.
  
  
  RESULTS
  Of a total of 5965 citations retrieved, 24 eligible studies were identified and reviewed, providing 1608 eyes with BRVO with data on natural history. Visual acuity (VA) was moderately poor at baseline (<20/40). Although VA generally improved, with mean improvement ranging from 1 letter at 6 weeks to 28 letters up to 24 months, few studies reported improvement beyond 20/40. Over a 1-year period, 5% to 15% of eyes developed macular edema (ME), but of those with ME at baseline, 18% to 41% resolved. At baseline, 5% to 6% of eyes had bilateral BRVO, with 10% developing fellow eye involvement over time. There were few high-quality studies on other outcomes, including development of new vessels.
  
  
  CONCLUSIONS
  Visual acuity generally improved in eyes with BRVO without intervention, although clinically significant improvement beyond 20/40 was uncommon.
authors.affiliation: Centre for Eye Research Australia, University of Melbourne, VIC, Australia.
authors.forename: Sophie L
authors.initials: SL
authors.lastname: Rogers
authors.forename: Rachel L
authors.initials: RL
authors.lastname: McIntosh
authors.forename: Lyndell
authors.initials: L
authors.lastname: Lim
authors.forename: Paul
authors.initials: P
authors.lastname: Mitchell
authors.forename: Ning
authors.initials: N
authors.lastname: Cheung
authors.forename: Jonathan W
authors.initials: JW
authors.lastname: Kowalski
authors.forename: Hiep P
authors.initials: HP
authors.lastname: Nguyen
authors.forename: Jie Jin
authors.initials: JJ
authors.lastname: Wang
authors.forename: Tien Yin
authors.initials: TY
authors.lastname: Wong
mesh_terms: D006801:Humans; D012169:Retinal Vein / Q000503:physiopathology; D012170:Retinal Vein Occlusion / Q000503:physiopathology*; D014792:Visual Acuity / Q000502:physiology