title: High Dk piggyback contact lens system for contact lens-intolerant keratoconus patients.
abstract: BACKGROUND
  The aim of the study was to examine the clinical success of high Dk (oxygen permeability) piggyback contact lens (PBCL) systems for the correction of contact lens intolerant keratoconus patients.
  
  
  METHODS
  Sixteen patients (29 eyes) who were not able to wear gas-permeable rigid lenses were included in this study. Hyper Dk silicone hydrogel (oxygen transmissibility or Dk/t = 150 units) and fluorosilicone methacrylate copolymer (Dk/t = 100 units) lenses were chosen as the PBCL systems. The clinical examinations included visual acuity and corneal observation by biomicroscopy, keratometer reading, and fluorescein staining before and after fitting the PBCL system.
  
  
  RESULTS
  INDICATIONS FOR USING PBCL SYSTEM WERE: lens stabilization and comfort, improving comfort, and adding protection to the cone. Visual acuities increased significantly in all of the patients compared with spectacles (P = 0). Improvement in visual acuity compared with rigid lenses alone was recorded in 89.7% of eyes and no alteration of the visual acuity was observed in 10.3% of the eyes. Wearing time of PBCL systems for most of the patients was limited time (mean 6 months, range 3-12 months); thereafter they tolerated rigid lenses alone except for 2 patients.
  
  
  CONCLUSIONS
  The PBCL system is a safe and effective method to provide centering and corneal protection against mechanical trauma by the rigid lenses for keratoconus patients and may increase contact lens tolerance.
authors.affiliation: Fatih Sultan Mehmet Training and Research Hospital, Istanbul, Turkey.
authors.forename: Tomris
authors.initials: T
authors.lastname: Sengor
authors.forename: Sevda Aydin
authors.initials: SA
authors.lastname: Kurna
authors.forename: Suat
authors.initials: S
authors.lastname: Aki
authors.forename: Yelda
authors.initials: Y
authors.lastname: Ozkurt