Flexure and residual astigmatism with RGP lenses of low, medium, and high oxygen permeability

Lens flexure and residual astigmatism were evaluated with rigid gas permeable (RGP) contact lenses made in low, medium, and high oxygen permeable (Dk) materials to determine if significant differences would be apparent as lens Dk was changed. Fourteen successful RGP contact lens wearers had their customary lens parameters, including lens thickness, held constant in duplicate pairs made in low (15), medium (60), and high (150) Dk materials. Flexure measured by keratometry over the lenses and residual astigmatism by sphero-cylindrical over-refraction were determined after a 1-week daily wearing period for each lens. No significant differences were found within or between lens materials when comparing magnitude of flexure and residual astigmatism by over-refraction. These results indicate that practitioners can expect lenses across the spectrum of Dk values, such as those evaluated in this study, to perform in a similar manner regarding lens flexure and residual astigmatism.