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From Vance Thompson Vision, Sioux Falls, South Dakota (JPB); Minnesota Eye Consultants, Minnetonka, Minnesota (DRH); University of Iowa Carver College of Medicine, Iowa City, Iowa (BAK); and Science in Vision, Akron, New York (RP).
Supported by an investigator-initiated research grant to Ocular Surgical Data, LLC, from Alcon (Fort Worth, TX).
Drs. Berdahl and Hardten are owners of Ocular Surgical Data, LLC, makers of <ext-link ext-link-type="uri" xlink:href="astigmatismfix.com" xlink:type="simple">astigmatismfix.com</ext-link>. Dr. Berdahl is a consultant to Alcon, AMO, and Bausch & Lomb. Dr. Hardten is a consultant to AMO, ESI, and TLCVision. Dr. Potvin is a consultant to Alcon, Haag-Streit, Imprimis, and Ocular Therapeutix. Mr. Kramer has no financial or proprietary interest in the materials presented herein.
Corneal astigmatism of a magnitude likely to be visually significant may be found in one-third of the population presenting for cataract surgery. 1 Implantation of toric intraocular lenses (IOLs) is one of the most successful methods of reducing the effect of this astigmatism on the postoperative refraction. 2 However, significant levels of residual refractive astigmatism after toric IOL implantation may be present in some patients and reduce uncorrected vision. After toric IOL implantation, the percent of eyes with residual astigmatism greater than 0.50 diopters (D) may be as high as 47%, but is more typically in the 20% to 30% range. 3 Understanding the reasons for such residual refractive astigmatism may help improve outcomes after toric IOL implantation.
Reasons for residual astigmatism that were previously explored included preoperative measurement or calculation errors, operative toric lens misalignment, and postoperative toric lens rotation. It is important to understand the impact that each of these has on refractive error after toric IOL implantation so that corrective methods can be applied effectively. The impact of preoperative measurements, mostly in the form of the corneal curvature readings from the anterior and posterior corneal surfaces, has been explored extensively in the literature and they are believed to play an important role in the amount of residual astigmatism after toric IOLs. 4-6 Toric calculator limitations have also been documented that may reduce the predictability of results. 7-9 Preoperative and intraoperative marking errors and anatomical characteristics of eyes with longer axial lengths are factors that might negatively affect the correct alignment of toric lenses; in highly myopic eyes,...