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Rotational stability and spherical aberration correction are key to high levels of outcomes with toric IOLs T wo key elements to success with toric IOLs include postoperative rotational stability and excellent visual outcomes. These elements set up the surgeon for the best chances of success with toric IOL patients. Rotational stability Rotation of a toric lens can have a significant impact on vision. For example, a 4-degree rotation under- corrects the astigmatism by about 14%. With a 16-degree rotation, one achieves only half the intended cylinder correction, while a 30-de- gree rotation results in no cylindri- cal correction at all. 1 We reviewed postoperative rota- tional stability in a recent prospec- tive, multicenter clinical trial of a new, single-piece, hydrophobic acrylic toric IOL called the Tecnis Toric IOL (Abbott Medical Optics, Santa Ana, Calif.). This study, con- ducted at 14 investigational sites in the U.S. and Canada, was designed to evaluate safety and effectiveness, including the ability to reduce astig- matism. A total of 174 first eyes were implanted with the lenses. Overall, >93% of all first eyes had a change in axis of ≤5 degrees between stability visits (1-3 months and 3-6 months). This matches up well with the recent standards set by the American National Standards Institute (ANSI), which require that ≥90% of eyes have ≤5 degrees axis change between visits 3 months apart. (See article by Daniel Chang, MD, on page 4). The mean axis change, taking direction into ac- count, was –1.35 degrees, and mean absolute change (regardless of direc- tion) was 2.74 degrees. The rotational stability of these lenses can be attributed to the three- point fixation with offset, forward- mounted, rigid haptics, as well as the long total diameter (13.0 mm) of the Tecnis Toric. Visual outcomes At six months, 97% of first eyes had monocular uncorrected distance visual acuity (UCDVA) of 20/40 or better; 41% were 20/20 or better. Best-corrected distance acuity (BCDVA) was 20/40 or better in all eyes. There was a 75% reduction in mean cylinder in the eyes implanted with the Tecnis Toric. Spectacle inde- pendence was also high with 80% reporting never needing to wear glasses for distance. I also find that the correction of spherical aberration permits an addi- tional degree of forgiveness, provid- ing surprisingly good acuity even in the occasional case of residual sphere and cylinder. Better correc- tion of SA provides crisper vision, making the lens more forgiving of minor power calculation errors. This becomes particularly important in the presence of disease processes characterized by a loss of contrast acuity, such as macular degeneration and epi-retinal membrane, where preserving contrast acuity is para- mount. In my opinion, toric IOLs represent the best option for excellent uncorrected distance vision in patients with more than 1.0 to 1.5 D of astigmatism. The more choices we have in toric lens technology, in terms of the material, design, and spherical aberration cor- rection, the better selection we can make for our astigmatic cataract pa- tients. Dr. Tyson is in private practice, Cape Coral Eye Center, Cape Coral, Fla. He can be contacted at 239-542-2020 or tysonfc@hotmail.com. References 1. Wolff J (2007) presented at AAD Congress, Duesseldorf, Germany 2. Artal P, Alcon E, Villegas E. Spherical aberration in young subjects with high visual acuity. Presented at: European Society of Cataract and Refractive Surgeons meeting, September 9-13, 2006; London. Paper 558. 3. Smith G, Cox MJ, Calver R, Garner LF. The spherical aberration of the crystalline lens of the human eye. Vision Res 2001;41:235-43. 5 by Farrell C. "Toby" Tyson II, MD, FACS Two keys for maximizing outcomes with toric IOLs " The more choices we have in toric lens technology, in terms of the material, design, and spherical aberration correction, the better selection we can make for our astigmatic cataract patients. " Farrell C. "Toby" Tyson II, MD, FACS Reduction of effectiveness as a toric lens is rotated Rotational stability data from the AMO toric IOL multicenter trial Source all: Farrell C. "Toby" Tyson II, MD, FACS EW San Francisco Update on the latest in refractive cataract techniques and technologies AMO Saturday supplement_SF2013-dl.qxp_Layout 1 4/19/13 11:27 PM Page 5

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