Zernike astigmatism and visual performance in myopic eyes by rigid gas permeable contact lenses wear

To investigate the effects of rigid-gas-permeable contact lens (RGP-CL) wear on Zernike astigmatism and visual performance in myopic eyes. Methods: A wavefront sensor was used to evaluate Zernike astigmatism for 21 eyes with minimum astigmatism and 18 eyes with moderate astigmatism under three different modes of refractive correction: the RGP-CL, spectacle lens correcting spherical equivalent (SL) and spectacle lens fully correcting spherical error and astigmatism (fSL). Contrast visual acuity was assessed with a VA tester at four contrast levels and two luminance backgrounds. Results: Compared to the SL wear, RGP-CL wear changed the main axis astigmatism (Z(2)(2)) from -0.09 +/- 0.34 to 0.34 +/- 0.22 for the minimum astigmatism group, while the contrast VA was improved about 0.05 LogMAR (F - 8.06, p < 0: 01). For the group with moderate astigmatism, significant reduction in Z(2)(2) was found for both fSL wear (t = 4.78, p < 0.001) and RGP-CL wear (t = 6.29, p < 0.0001). The changes in astigmatism were significantly correlated between the fSL and RGP-CL wears (r = 0.897, p < 0.0001 for Z(2)(-2); and r = 0.643, p = 0.004 for Z(2)(2)). Contrast VA was significantly improved for both fSL and RGP-CL wears and the improvements were significantly correlated between each other for all four contrast levels and two backgrounds. Conclusion: RGP-CL wear induces astigmatism for the eyes with minor astigmatism probably due to a correction of corneal astigmatism and thus a manifesting of the lens astigmatism. For the astigmatic eyes, RGP-CL wear has similar effect on correcting astigmatism as the spectacle lens wear with spherical-cylinder correction and also produces similar visual improvement.