Rigid gas-permeable extended wear: a comparative clinical study

Abstract

A 12-month clinical trial involving 88 subjects was undertaken to compare the clinical performance of rigid gas-permeable contact lens extended wear (EWRGP) with that of RGP daily wear (DWRGP) lenses and soft lens extended wear (SLEW) with medium water content lenses. Withdrawals from the EWRGP group tended to result from lens-related problems, whereas the SLEW withdrawals generally resulted from adverse effects on corneal physiology. Changes in spherical refractive error during the 1-year study were small (less than 1.00 D) and similar for both gas-permeable lens-wearing groups. Most of the SLEW group (58%) showed an increase in myopia and the mean increase was 0.38 D, which represented a significant difference from the EWRGP group. The EWRGP group showed a mean flattening in corneal curvature of 0.11 and 0.15 mm in the flattest and steepest corneal meridians, respectively. A positive correlation was noted between change in corneal curvature and baseline corneal astigmatism, which suggests corneal molding as a result of lid pressure as the most likely cause. The DWRGP and SLEW groups showed small, nonsignificant changes in corneal curvature. Most of the EWRGP subjects (69%) who completed the study showed increased corneal distortion. This compares with 30 and 17% with the DWRGP and SLEW groups, respectively. Likely corneal edema was a major contributory factor. For most of the slitlamp variables monitored, there were no significant differences between the groups. However, microcystic changes were detected in both EWRGP (35%) and SLEW subjects but not in the DWRGP group. Corneal staining was noted in all groups but was more prevalent among the EWRGP group. The findings of this study are discussed in relation to the clinical management of RGP extended wear.