title: Causal models in primary open angle glaucoma.
abstract: OBJECTIVE
  To apply three of the most common epidemiologic causal models for glaucoma and explain the issues pertaining to the use of them.
  
  
  METHODS
  Three causal models will be explained: (1) counterfactual model, (2) graphical model, and (3) sufficient-component causal model. Using literature search and experts' opinions these models will be applied in glaucoma.
  
  
  RESULTS
  Introducing the counterfactual model, as one of the most important quantitative causal models and formalizes the concepts of cause and effect, this article emphasizes the limitations with the use of this model for glaucoma. Explaining causal diagram, as a useful qualitative tool that provides a lucid depiction of the assumptions concerning a causal pathway, this article provides a working causal diagram for glaucoma based on the evidence in the literature and experts' comments. In addition, the limitations in developing appropriate causal diagrams for glaucoma are discussed. Finally, the sufficient-component causal models and their importance in portraying the mechanics of causal interactions will be discussed.
  
  
  CONCLUSIONS
  Paucity of evidence is the main issue with the use of causal models for glaucoma. This article calls for convergent review of different theories and different pieces of evidence that can enable us to apply different causal models for glaucoma.
authors.affiliation: Department of Ophthalmology, Johns Hopkins Schools of Medicine and Public Health, Johns Hopkins University, Baltimore, MD, USA. hbahrami@jhsph.edu
authors.forename: Hossein
authors.initials: H
authors.lastname: Bahrami
mesh_terms: D015984:Causality; D005902:Glaucoma, Open-Angle / Q000453:epidemiology* / Q000503:physiopathology; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D008962:Models, Theoretical; D012720:Severity of Illness Index