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Supported by unrestricted educational grants from Abbott Medical Optics, Alcon Laboratories, and Bausch + Lomb Pearls for achieving surgical success with toric IOLs Douglas D. Koch, MD To ensure patient satisfaction, surgeons must be prepared to refine postoperative outcomes if necessary I mplantation of toric in- traocular lenses (IOLs) is more than a procedure—it is a comprehensive process, said Douglas D. Koch, MD. Surgeons must take critical steps before, during, and after surgery to ensure precise visual outcomes and patient satisfaction. Causes of error Regardless of surgeons' experi- ence, surgical outcomes occasion- ally fall short, Dr. Koch said. There are many causes. Preoperative measurements may be imperfect (Figure 1). Intra- operatively, misalignment can occur, Dr. Koch said. Marks may be blunt or imprecisely located, and there may be parallax as the surgeon examines the lens. Furthermore, surgically induced astigmatism (SIA) may vary because of the wound con- struction and location, as well as the patient's biologic features (Figure 2). The effects of relaxing incisions also may differ. "Postoperatively, the IOL can rotate," he said. In addition, a spherical error may occur. Additional treatments After surgery, patients with mono- focal IOLs may require additional treatment if residual astigmatism is 0.75 D or greater, depending on their visual needs, Dr. Koch ex- plained. 1 "With a multifocal IOL … we have to be much tighter, reducing astigmatism to less than 0.5 D," he said. Hayashi et al. reported that patients had 20/20 vision at distance if astigmatism was 0 after implantation of an AcrySof ReSTOR IOL with a +3.0 D add (Alcon, Fort Worth, Texas), but if they had 0.5 D of astigmatism, their vision decreased to 20/30. 2 When making postoperative adjustments, surgeons need to consider the alignment of the IOL, whether they have under- or overcorrected the astigmatism, the magnitude of the error, and the IOL power accuracy, Dr. Koch said. If the IOL power is incorrect, he recommended an excimer laser ablation or IOL exchange, depending on the magnitude of the error. He suggested an IOL ex- change for larger residual errors, especially on the hyperopic side. If the spherical power is correct, the IOL is aligned, and astigmatism is within 1.25 D, he performs a peripheral corneal relaxing incision if it was not per- formed previously. He takes this approach regardless of whether astigmatism is under- or over- corrected. "If there are existing relaxing incisions, you can either reopen them, enlarge them, or even consider making another one," he said. If astigmatism is 1.5 D or greater, he recommends considering excimer laser ablation or IOL exchange. If the IOL is misaligned and astigmatism is 1.0 to 1.25 D, he again prefers relaxing incisions. If it exceeds 1.25 D, the Toric Results Analyzer developed by John Berdahl, MD, and David Hardten, MD, is a helpful tool (astigmatismfix.com). Conclusion "Astigmatism correction is a process with our patients," Dr. Koch said. "There are critical steps before, during, and after surgery. It's mandatory to be prepared to adjust your patients postopera- tively in order to provide them with optimal outcomes. Fortu- nately, we have excellent options available to us, thanks to things like astigmatismfix.com and techniques as simple as relaxing incisions." References 1. Villegas EL, Alcón E, Artal P. Minimum amount of astigmatism that should be corrected. J Cataract Refract Surg. 2014; 40:13–19. 2. Hayashi K, Manabe S, Yoshida M, Hayashi H. Effect of astigmatism on visual acuity in eyes with a diffractive multifocal intraocular lens. J Cataract Refract Surg. 2010; 36(8):1323–1329. Dr. Koch is a professor and the Allen, Mosbacher, and Law chair in ophthalmolo- gy, Cullen Eye Institute, Baylor College of Medicine, Houston. He can be contacted at dkoch@bcm.edu. 7 Figure 1. Dual Scheimpflug Placido map of a patient with a large amount of anterior and posterior corneal astigmatism; ignoring or misestimating the latter can result in suboptimal uncorrected acuity. Figure 2. Dr. Koch's SIA in a series of eyes

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