JUL 01, 2006
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.
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).
Courtesy Advanced Medical Optics.
Figure 1. Tecnis IOL.
The clinical investigation of the Tecnis IOL submitted to the U.S. Food and Drug Administration (FDA) demonstrated elimination of mean spherical aberration as well as significant improvement in functional vision when compared to a standard spherical IOL.3 The U.S. Centers for Medicare and Medicaid Services announced New Technology IOL Status for the Tecnis IOL on January 26, 2006.
AcrySof IQ. The AcrySof IQ shares the ultraviolet (UV) and blue light-filtering chromophores as those found in the single-piece, acrylic AcrySof Natural IOL. The special feature of this IOL is the posterior aspheric surface, which is designed to compensate for spherical aberration by addressing the effects of over-refraction at the periphery. The AcrySof IQ is a single-piece lens made of hydrophobic acrylic, and it has a refractive index of 1.55. It adds -0.20 µ of spherical aberration to the eye (Figure 2).
Courtesy Mark Packer, MD.
SofPort Advanced Optics. The SofPort Advanced Optics (LI61AO) IOL is an aspheric IOL that has been specifically designed with zero spherical aberration, so that it will not contribute to any preexisting higher-order aberrations. It is a foldable silicone IOL with polymethylmethacrylate (PMMA) haptics and square edges. It was specifically designed for use with the Bausch & Lomb SofPort System, an integrated, single-use, single-handed planar delivery IOL insertion system. The SofPort lens is a multi-piece lens made of second-generation silicone. It has a refractive index of 1.43, and it introduces no spherical aberration to the eye (Figure 3).
Courtesy Mark Packer, MD.
Figure 3. Advanced Optic IOL.
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Dr. Packer states that he is a consultant for Advanced Medical Optics (AMO) and Bausch & Lomb, and that he has received travel support and honoraria from Alcon. He has no financial interest in any of the products or procedures described in this article.