title: Refractive errors and age-related macular degeneration: a systematic review and meta-analysis.
abstract: OBJECTIVE
  To evaluate the association between refractive errors and age-related macular degeneration (AMD).
  
  
  METHODS
  A clear understanding of the relationship between refractive error and AMD provides insights into the pathophysiology of AMD.
  
  
  METHODS
  We searched PubMed and Embase from their inception to July 2012 for population-based studies with data on refractive error and AMD assessed from retinal photographs at baseline and follow-up. We performed separate meta-analyses for cross-sectional studies and cohort studies using adjusted odds ratios (ORs) and hazard ratios (HRs) under random effects models, respectively.
  
  
  RESULTS
  Analysis of the 6 cross-sectional studies showed that hyperopia was associated with higher odds of prevalent AMD (pooled OR hyperopia vs. emmetropia: 1.16; 95% confidence interval [CI], 1.04-1.29) and that myopia was associated with lower odds of prevalent AMD (pooled OR myopia vs. emmetropia: 0.75; 95% CI, 0.61-0.92). Analysis from the 3 cohort studies showed nonsignificant associations. Analysis of the 5 cross-sectional and 2 cohort studies showed that each diopter increase in spherical equivalent was associated with increased odds of both prevalent (pooled OR, 1.09; 95% CI, 1.06-1.12) and incident (pooled HR, 1.06; 95% CI, 1.02-1.10) AMD. In 3 cross-sectional studies with data on axial length, each millimeter increase in axial length was associated with a decreased odd of prevalent AMD (pooled OR, 0.76; 95% CI, 0.69-0.85).
  
  
  CONCLUSIONS
  Refractive error is associated with AMD, although a temporal relationship cannot be determined on the basis of current evidence. Ophthalmologists should be aware that risk of AMD clinically seems to vary by refractive status.
  
  
  BACKGROUND
  The author(s) have no proprietary or commercial interest in any materials discussed in this article.
authors.affiliation: Saw Swee Hock School of Public Health, National University of Singapore, Singapore.
authors.forename: Chen-Wei
authors.initials: CW
authors.lastname: Pan
authors.forename: M Kamran
authors.initials: MK
authors.lastname: Ikram
authors.forename: Carol Y
authors.initials: CY
authors.lastname: Cheung
authors.forename: Hyung-Won
authors.initials: HW
authors.lastname: Choi
authors.forename: Chiu-Ming Gemmy
authors.initials: CM
authors.lastname: Cheung
authors.forename: Jost B
authors.initials: JB
authors.lastname: Jonas
authors.forename: Seang-Mei
authors.initials: SM
authors.lastname: Saw
authors.forename: Tien-Yin
authors.initials: TY
authors.lastname: Wong
mesh_terms: D006801:Humans; D008268:Macular Degeneration / Q000150:complications*; D012030:Refractive Errors / Q000209:etiology*