title: [Evidence based ophthalmology: critical appraisal skills on clinical trials on treatments].
abstract: OBJECTIVE
  To analyse and provide the tools to answer three questions that must be asked about a clinical trial on treatments: evaluation of validity (internal validity, so that results are not biased); clinical importance of these results and their application to individual patients. We provide simple statistics tools, clinical trial design, and clinical epidemiology for the evaluation and analysis of clinical trials on treatments.
  
  
  METHODS
  Review of the medical literature.
  
  
  RESULTS
  For the evaluation of papers on treatment and for using a treatment efficiently, we need to know if the clinical trials that support it are trustworthy, if the treatment has clinical importance and if it can be applied to my patients.
  
  
  CONCLUSIONS
  It is of paramount importance to check that the sample of the clinical assay has been correctly randomized, because randomization is necessary to comply with mathematical laws of application of statistical tests. Follow-up of patients must be complete in order to measure precision of results and evaluate the efficacy of treatment.
authors.affiliation: Servicio de Oftalmología, Hospital Esperit Sant, Santa Coloma de Gramenet, Barcelona, Spain. jcarlosmesa@mixmail.com
authors.forename: J C
authors.initials: JC
authors.lastname: Mesa-Gutiérrez
authors.forename: A
authors.initials: A
authors.lastname: Rouras-López
authors.forename: I
authors.initials: I
authors.lastname: Cabiró-Badimón
authors.forename: V
authors.initials: V
authors.lastname: Amías-Lamana
authors.forename: J
authors.initials: J
authors.lastname: Porta-Monnet
mesh_terms: D002986:Clinical Trials as Topic / Q000592:standards*; D019317:Evidence-Based Medicine; D006801:Humans; D009885:Ophthalmology / Q000592:standards*; D015203:Reproducibility of Results; D013812:Therapeutics