In vivo dehydration of silicone hydrogel contact lenses.
OBJECTIVE
To benchmark the performance of new-generation silicone hydrogel contact lenses in terms of their in vivo hydration characteristics and to highlight the possible clinical ramifications of any changes observed.


METHODS
Thirteen subjects (four men and nine women with a mean age of 24.8 +/- 5.0 years) wore a silicone hydrogel lens (PureVision, Bausch & Lomb, Rochester, NY) in one eye and a conventional hydrogel lens (ACUVUE 2, Johnson & Johnson Vision Care, Jacksonville, FL) in the other eye for 4 weeks on an extended-wear basis. A gravimetric method was used to determine lens water content and dehydration during the intended lifespan of the lenses.


RESULTS
For the PureVision lens, the water content was 38.3% +/- 0.9%, 35.2% +/- 1.1%, and 35.3% +/- 1.7% at baseline and after 2 and 4 weeks of wear, respectively (F=28.4, P<0.0001). For the ACUVUE 2 lens, the water content was 58.1% +/- 0.6% and 52.1% +/- 1.3% at baseline and after 2 weeks of wear, respectively. Thus, after 2 weeks of wear, absolute dehydration was 2.8% +/- 1.8% and 6.0% +/- 1.3% for the PureVision and ACUVUE 2 lenses, respectively (t=6.8, P<0.0001). The mass of deposition was calculated to be 568 +/- 457 microg for the PureVision lens and 1,660 +/- 499 microg for the ACUVUE 2 lens (t=5.1, P=0.0003).


CONCLUSIONS
The ACUVUE 2 lens underwent a greater degree of lens dehydration, causing a reduction in oxygen permeability (3.6 barrer), and deposition after 2 weeks of extended wear. The loss of water from the PureVision lens was paradoxically associated with a 6.0-barrer increase in oxygen permeability after 4 weeks of extended wear.
Morgan
Philip B
PB
Eurolens Research, Dapartment of Optometry, University of Manchester Institute of Science and Technology, Manchester, United Kingdom. philip.morgan@umist.ac.uk
Efron
Nathan
N
D000328:Adult; D019985:Benchmarking; D001672:Biocompatible Materials; D003262:Contact Lenses, Extended-Wear; D003890:Desiccation; D005260:Female; D006801:Humans; D008297:Male; D010100:Oxygen / Q000378:metabolism; D010539:Permeability; D012826:Silicone Elastomers; D014867:Water / Q000378:metabolism
D001672:Biocompatible Materials; D012826:Silicone Elastomers; D014867:Water; D010100:Oxygen