Optical quality of hydrogel ophthalmic devices created with femtosecond laser induced refractive index modification

The wavefront aberrations of hydrogel material were altered using a technique of femtosecond laser induced refractive index modification. Gradient-index Fresnel lenses ranging from −3.0 to +1.5 diopters (5.8 mm diameter) were written in contact lens material (Contaflex GM Advance 58). Optical quality was assessed in terms of wavefront aberrations, image contrast, and scatter. The spherical and cylindrical power writing errors were 0.05 D ± 0.07 D and 0.10 D ± 0.14 D respectively, and the lenses preserved almost all spatial frequency information relevant for human vision. The induced wavefronts were comprised of a mosaic of approximately 1400 stitched segments, leading to undesirable diffraction. This work demonstrates the capability of femtosecond laser induced refractive index modification to produce high quality optical devices for vision correction.