JUL 01, 2006
Cataract/Anterior Segment
Because the optical wavefront of the cornea remains essentially stable throughout life,1 refractive lens exchange appears to represent a permanent solution to the challenges of restoring accommodation and achieving youthful quality of vision. To that end, recent advances in aspheric monofocal lens design have lent themselves to improvements in multifocal and accommodative intraocular lenses (IOLs), as attention has turned to the development of aspheric IOLs to remedy the increase in total optical aberrations that result from the positive spherical aberration of a spherical pseudophakic IOL.2 These designs are intended to reduce or eliminate the spherical aberration of the eye, improve modulation transfer function as compared with a spherical pseudophakic implant, and enhance functional vision. A variety of aspheric IOL designs are currently marketed in the United States: the Tecnis Z9000 IOL, the AcrySof IQ IOL, and the SofPort AO IOL.
Comparing Lenses
Tecnis Z9000. The Tecnis IOL was designed with a modified prolate anterior surface to compensate for the average corneal spherical aberration found in the adult eye. It shares basic design features with the CeeOn 911A IOL including a 6-mm, biconvex, square-edge optic and angulated “capsular C” polyvinylidene fluoride (PVDF) haptics. The Tecnis Z9000 is a multi-piece lens. It is available in both second-generation silicone and acrylic. The silicone IOL has a refractive index of 1.46, and the acrylic lens has a refractive index of 1.47. The Tecnis Z9000 introduces -0.27 µ of spherical aberration to the eye (Figure 1).