title: An epidemiologic investigation of unexpected refractive errors following cataract surgery.
abstract: OBJECTIVE
  To determine the extent and magnitude of unexpected refractive errors following cataract surgery with intraocular lens (IOL) implantation and to determine what characteristics were associated with the errors.
  
  
  METHODS
  In this nonconcurrent prospective study, preoperative, intraoperative and postoperative information was collected from the charts of the 523 consecutive patients who underwent cataract extraction and polymethylmethacrylate IOL implantation performed by one of nine participating surgeons between Jan. 1 and Apr. 30, 1995, or the same dates in 1996.
  
  
  METHODS
  University-affiliated eye care centre in Vancouver.
  
  
  METHODS
  Postoperative excess correction, calculated for each patient by subtracting the actual postoperative spherical equivalent from the expected spherical equivalent. Eyes with an excess correction of more than 1.00 dioptre were considered "overcorrected."
  
  
  RESULTS
  Univariate analysis showed that the formula used to calculate the lens power, axial length, year of surgery, A-constant/surgeon factor used and lens manufacturer were associated with overcorrection. In a logistic regression model, lens manufacturer was the only variable independently associated with overcorrection.
  
  
  CONCLUSIONS
  Routine reporting and follow-up is necessary to identify this kind of "outbreak" and the associated factors. The current guidelines of the Health Protection Branch, Health Canada, for evaluation of IOLs that have changed manufacturers are not adequate to identify the kind of error that we detected.
authors.affiliation: British Columbia Centre for Epidemiologic and International Ophthalmology, University of British Columbia, St. Paul's Hospital, Vancouver. pcourtright@stpaulshosp.bc.ca
authors.forename: P
authors.initials: P
authors.lastname: Courtright
authors.forename: K
authors.initials: K
authors.lastname: Paton
authors.forename: J M
authors.initials: JM
authors.lastname: McCarthy
authors.forename: L M
authors.initials: LM
authors.lastname: Sibley
authors.forename: S P
authors.initials: SP
authors.lastname: Holland
mesh_terms: D000368:Aged; D001955:British Columbia / Q000453:epidemiology; D002387:Cataract Extraction / Q000009:adverse effects*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular / Q000009:adverse effects* / Q000592:standards; D008297:Male; D019904:Polymethyl Methacrylate; D011446:Prospective Studies; D012029:Refraction, Ocular; D012030:Refractive Errors / Q000453:epidemiology / Q000209:etiology*
chemical_list: D019904:Polymethyl Methacrylate