title: The ocular response to extended wear of a high Dk silicone hydrogel contact lens.
abstract: OBJECTIVE
  A four-month extended wear clinical trial was conducted to compare the ocular effects of a high Dk Balafilcon A silicone hydrogel lens and a low Dk HEMA 38.6 per cent H20 soft lens.
  
  
  METHODS
  Twenty-four subjects who were adapted to daily wear of soft lenses wore a high Dk lens in one eye and a low Dk HEMA lens in the other eye for four months on an extended wear basis after one week of daily wear. Thirteen progress evaluations were conducted using standard clinical procedures.
  
  
  RESULTS
  Eighteen subjects (75 per cent) completed the study. The high Dk lens induced significantly less bulbar and limbal injection and corneal vascularisation than the low Dk HEMA lens (p < 0.05). Epithelial microcysts were observed only in the eyes wearing the low Dk lens. A significant increase in myopia was found in the eyes wearing the low Dk HEMA lens (mean = 0.50 D, p < 0.01) compared to the insignificant myopic increase of 0.06 D in the eyes wearing the high Dk lens. Three subjects developed small infiltrates in the high Dk lens wearing eyes and significantly more post-lens debris was observed under the high Dk lens. Six subjects developed papillary conjunctivitis in the eye wearing silicone hydrogel lenses but only two of those were discontinued from the study.
  
  
  CONCLUSIONS
  No hypoxia-related effects were observed with extended wear of the high Dk Balafilcon A silicone hydrogel lens.
authors.affiliation: Centre for Contact Lens Research, School of Optometry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada.
authors.forename: Desmond
authors.initials: D
authors.lastname: Fonn
authors.forename: Karen E
authors.initials: KE
authors.lastname: MacDonald
authors.forename: Doris
authors.initials: D
authors.lastname: Richter
authors.forename: Nicola
authors.initials: N
authors.lastname: Pritchard
mesh_terms: D000328:Adult; D003262:Contact Lenses, Extended-Wear; D003315:Cornea / Q000502:physiology*; D003941:Diagnostic Techniques, Ophthalmological; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D008297:Male; D010100:Oxygen / Q000378:metabolism; D010539:Permeability; D012826:Silicone Elastomers; D014792:Visual Acuity
chemical_list: D012826:Silicone Elastomers; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D010100:Oxygen