Oxygen transmissibility and hydration of new and used hydrogel contact lenses

The oxygen transmissibility and hydration of new and used CSI, Hydrocurve II, and Hydromarc hydrogel contact lenses was determined at 37 degrees C. coatings that accumulated on used lenses were observed against a bright light and were graded in four classes from mild to severe. Some coated lenses had a statistically significant increase, and some a decrease in oxygen transmissibility compared with uncoated lenses. These differences are clinically unimportant, however. Although there seems to be a trend toward increased hydration and oxygen transmissibility with increased lens coating, statistically these relationships were found not to be linear. Failure of contact lenses after long-term wear must be due to causes other than a decrease in their oxygen transmissibility.