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A long term study of the water content changes in three types of hydrogel contact lenses

1 May 1987


Sufficient oxygen is required to pass through a hydrogel contact lens for proper corneal metabolism. The permeability of oxygen through such a lens is determined by its specific water content. Thus, it follows that if a hydrogel lens has a decrease in water content there will be a proportional decrease in the amount of oxygen available to the cornea through that lens. Changes in the water content of a lens also affect other important lens parameters. This study addressed the change in water content of three lens types: a low water content, CSI-T lens, (n=20); a medium water content, Hydrocurve II lens, (n=25); and a high water content, Permaflex lens, (n=14). Although studies of lens water content have been done before, none have followed the same lens wearers for an extended period of time while the lenses were being measured with a hand refractometer. This apparatus has been shown to be reliable, accurate, and non-lens damaging. Water content was measured at ten specific intervals from before lens wear to Day 160. Analysis of the data demonstrated that all three lens types showed a statistically significant decrease in water content. After the 30 minute measurement interval, however, the percent change in water content was very slight. Although there were a few statistically significant points after the 30 minute point, none were deemed to be of clinical relevance.


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