title: Recovery from hyperemia after overnight wear of low and high transmissibility hydrogel lenses.
abstract: OBJECTIVE
  To measure the limbal vascular response after 8 hours of eye closure while wearing high and low permeability lenses compared to control eyes without lenses.
  
  
  METHODS
  Twenty neophyte participants wore lotrafilcon A silicone hydrogel lenses (HDk; Dk = 140) or etafilcon A hydrogel lenses (LDk; Dk = 18). On two different nights the lenses were randomly worn for 8 hours during sleep in the right eyes only. Left eyes were non-lens wearing controls. Biomicroscopic images of the temporal limbal area were videotaped at baseline, on eye opening and every 20 minutes for 3 hours. A masked observer graded digitized images of the limbal area.
  
  
  RESULTS
  On waking and after lens removal there were no differences in hyperemia between the HDk and LDk lens wearing eyes. There were also no differences at any time between the HDk lens wearing eyes and their control eyes (p > 0.05). On waking the eyes wearing the LDk lens were more hyperemic compared to baseline (p < 0.001) and compared to their control eyes at 20 (p < 0.001) and 180 minutes (p = 0.01), indicating slower recovery from hyperemia. The HDk lens wearing eyes recovered to their baseline levels by 180 minutes (p = 0.99), compared to the LDk lens wearing eyes, which had not recovered to baseline levels by 180 minutes (p = 0.04).
  
  
  CONCLUSIONS
  The reduction in hyperemia over time of the HDk lens wearing eyes was the same as the controls. The LDk lens wearing eyes were more hyperemic than the controls on waking and the reduction in hyperemia over time was slower. This suggests that the slower recovery from hyperemia may be affected by the lower oxygen transmissibility of the LDk lens.
authors.affiliation: Centre for Contact Lens Research, School of Optometry, University of Waterloo, Canada.
authors.forename: R
authors.initials: R
authors.lastname: du Toit
authors.forename: T L
authors.initials: TL
authors.lastname: Simpson
authors.forename: D
authors.initials: D
authors.lastname: Fonn
authors.forename: R L
authors.initials: RL
authors.lastname: Chalmers
mesh_terms: D000328:Adult; D003263:Contact Lenses, Hydrophilic; D005260:Female; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D006940:Hyperemia / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*; D000860:Hypoxia / Q000378:metabolism / Q000503:physiopathology; D016850:Limbus Corneae / Q000098:blood supply*; D008297:Male; D010100:Oxygen / Q000378:metabolism
chemical_list: D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D010100:Oxygen