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.

Wavefront reconstruction algorithm for wavefront sensing based on binary aberration modes

We propose a new algorithm for wavefront sensing based on binary intensity modulation. The algorithm is based on the fact that a wavefront can be expended with a series of orthogonal and binary functions, the Walsh series. We use a spatial light modulator（SLM） to produce different binary-intensity-modulation patterns which are the simple linear transformation of the Walsh series. The optical fields under different binary-intensity-modulation patterns are detected with a photodiode.The relationships between the incident wavefront modulated with the patterns and their optical fields are built to determinate the coefficients of the Walsh series. More detailed and strict relationship equations are established with the algorithm by adding new modulation patterns according to the properties of the Walsh functions. An exact value can be acquired by solving the equations. Finally, with the help of phase unwrapping and smoothing, the wavefront can be reconstructed. The advantage of the algorithm is providing an analytical solution for the coefficients of the Walsh series to reconstruct the wavefront. The simulation experiments are presented and the effectiveness of the algorithm is demonstrated.