Corneal thickness in daily contact lens wear. A comparison of a low water content lens and a high water content lens.

The corneal responses to daily wear of Scanlens 75 high water content lenses, average centre thickness 0.23 mm, and of Bausch & Lomb Soflens U3 low water content lenses, centre thickness 0.07 mm, were compared. Calculations of oxygen transmissibility indicated that corneal swelling might be less for the former lenses than for the latter lenses. This assumption was proved to be correct. The average increase in corneal centre thickness over the day (14 h) during a 4 week period was 1.6% for Scanlens 75 and 2.8% for Soflens U3. This difference was statistically highly significant (P less than 0.001). The thickness increase was greatest during the first week. Tests with thicker lenses showed that the thicker the lenses are, the more important it is to choose high water content lenses. The closed eye period increased corneal swelling in extended lens wear. The results favour a program based on certain high water content lenses and a daily wear schedule.