It is a very exciting time in cataract surgery. We have access to a wonderful array of IOLs that enable us to restore patients' high-quality vision while minimizing or even eliminating their dependence on spectacles. The diversity of these new IOLs also promotes customized solutions. Presbyopia-correcting lenses significantly improve our ability to help patients seeking spectacle independence at all distances without a compromise in their distance vision. Toric IOLs offer spectacle independence for distance to patients who are not optimal candidates for a multifocal IOL because of high amounts of corneal astigmatism or macular pathology. The FDA recently approved the Tecnis Toric IOL (Abbott Medical Optics Inc.). It combines the stability and precision of astigmatic correction with the proven platform of the wavefront-designed Tecnis aspheric IOL (Figure). Like other IOLs in the Tecnis family, the toric version reduces spherical aberration to near zero, which has been shown to improve functional vision most notably by speeding up drivers' reaction time in a night-driving simulation.1 This hydrophobic acrylic lens has the lowest chromatic aberration of IOLs tested,2 and its clear optic allows full transmission of healthy blue light to the retina.
The IOL's offset, forward-mounted haptics contact the capsular bag at three points, which should augment its long-term stability, refractive predictability, and centration. The square posterior optic edge of the lens provides uninterrupted contact between the posterior surface of the optic and the anterior surface of the posterior capsule.
ASTIGMATIC CORRECTION AND STABILITY
The Tecnis Toric lens allows precise astigmatic correction while its correction of spherical aberration provides sharper quality of vision than IOLs with less compensation for spherical aberration.3 The IOL's design also limits lens epithelial cell migration,4,5 which reduces the chance of posterior capsular opacification.
This toric lens is available in a wide spectrum of cylindrical powers (1.50, 2.25, 3.00 D; 4.00 D of cylindrical power at the IOL plane and spherical powers of +5.00 to +34.00 D in 0.50 D increments) to address preexisting corneal astigmatism of at least 1.00 D in adults who have undergone cataract extraction. Selecting the correct lens model and axial placement is made quite simple by the manufacturer's IOL calculator (www.tecnistoriccalc.com).
MULTIFOCAL AND TORIC IOLs IN PRACTICE
In my practice, every initial workup of a cataract patient is the same. It includes corneal topography so that I may intelligently discuss lens options during the consultation. If the patient is interested in maximizing his or her spectacle independence and has no ocular pathology that will prevent optimal results, then I will recommend the Tecnis Multifocal (Abbott Medical Optics Inc.). Its fully diffractive posterior surface makes the optic less pupil dependent, which is especially important for mesopic reading conditions. In my experience, the Tecnis Multifocal's optics provide patients with very good near and distance vision across a range of lighting conditions.
When patients have relatively low but still visually significant astigmatism, I implant the multifocal IOL and perform limbal relaxing incisions to address the cylinder. I can confidently treat up to 2.00 D of astigmatism with this approach. When patients with greater than 2.00 D of astigmatism desire spectacle-free distance and near vision, I will still offer a Tecnis Multifocal lens, but I educate them about their expected suboptimal results in the immediate postoperative period (secondary to residual astigmatism) and their need for LASIK or PRK about 3 to 4 months postoperatively when their residual refractive error stabilizes. For many patients, this path is acceptable, because it can ultimately lead to spectacle-free near and distance vision for the rest of their lives once they reach postoperative month 4. To others (a minority), this course sounds too prolonged or involved. They opt for the toric IOL in order to obtain optimal spectacle-free distance vision right away, and they understand that they will remain dependent on reading glasses for the rest of their lives.
In my experience, for patients who are not ideal candidates for a multifocal lens and who have a visually significant amount of corneal astigmatism, the Tecnis Toric lens represents an option that will optimize their distance vision without spectacles in a precise and reproducible manner.
William K. Christian, MD, is in private practice at the Assil Eye Institute in Beverly Hills, California. He is a consultant to Abbott Medical Optics Inc. Dr. Christian may be reached at (310) 651-2300; firstname.lastname@example.org.
- Tecnis Foldable Posterior Chamber Intraocular Lens [package insert]. Santa Ana, CA: Abbott Medical Optics, Inc; 2009.
- Zhao H, Mainster MA. The effect of chromatic dispersion on pseudophakic optical performance. Br J Ophthalmol. 2007;91(9):1225-1229.
- Terwee T, Weeber H, van der Mooren M, Piers P. Visualization of the retinal image in an eye model with spherical and aspheric, diffractive, and refractive multifocal intraocular lenses. J Refract Surg. 2008;24(3):223- 232.
- Sacu S, Menapace R, Buehl W, et al. Effect of intraocular lens optic edge design and material on fibrotic capsule opacification and capsulorhexis contraction. J Cataract Refract Surg. 2004;30:1875-1882.
- Peng Q, Visessook N, Apple DJ, et al. Surgical prevention of posterior capsule opacification. Part 3: Intraocular lens optic barrier effect as a second line of defense. J Cataract Refract Surg. 2000;26(2):198-213.