title: Empirical fitting of soft or rigid gas-permeable contact lenses for the correction of moderate to severe refractive astigmatism: a comparative study.
abstract: BACKGROUND
  This study aims to validate the fitting of contact lenses derived from refractive and keratometric values in a group of subjects with moderate (2.50 diopters [D] to 5.00 D) to severe (>5.00 D) astigmatism. It aims also to show whether soft or rigid gas-permeable (GP) contact lenses offer the best correction and to determine which modality is preferred by subjects.
  
  
  METHODS
  Twenty subjects were randomly fitted with both soft and GP lenses. Group A was first fitted with soft lenses then switched to GPs and vice versa for group B. For each type of lens worn, low- and high-contrast visual acuity (VA) and stereoscopy were evaluated at both near and far. Each subject was asked to select the lens type of choice and to rate quality of vision in day-to-day activities through a questionnaire.
  
  
  RESULTS
  There was no significant difference in objective binocular VA between current spectacles and empirically calculated soft toric lenses and GP toric/bi-toric contact lenses at all distances. That was also true for stereoscopy. Subjectively, most of the subjects preferred rigid contact lenses because of the quality of their vision in day-to-day activities, and a majority of them decided to continue with that modality.
  
  
  CONCLUSIONS
  Empirical fitting of toric soft or GP contact lenses leads to very good results, which suggests that each type of lens might constitute a viable option.
authors: Université de Montréal, Ecole D'optométrie, Montreal, Canada. langis.michaud@umontreal.ca
authors: Langis
authors: L
authors: Michaud
authors: Cynthia
authors: C
authors: Barriault
authors: Annie
authors: A
authors: Dionne
authors: Peter
authors: P
authors: Karwatsky
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000503:physiopathology* / Q000534:rehabilitation*; D003261:Contact Lenses; D003263:Contact Lenses, Hydrophilic; D018592:Cross-Over Studies; D005139:Eyeglasses; D005740:Gases; D006801:Humans; D010539:Permeability; D017755:Prosthesis Fitting / Q000379:methods* / Q000592:standards*; D012720:Severity of Illness Index; D014792:Visual Acuity
chemical_list: D005740:Gases