2020–2021 BCSC Basic and Clinical Science Course™
13 Refractive Surgery
Chapter 8: Intraocular Refractive Surgery
Toric Intraocular Lenses
Complications Specific to Toric Intraocular Lenses
The primary complication of toric IOLs is the possibility of IOL rotation resulting in a misalignment of the astigmatic correction. Full correction is not achieved unless the IOL is properly aligned in the axis of astigmatism. Astigmatism calculations have shown that every 10° off-axis rotation of the lens reduces the correction by approximately one-third. Thus, at 30° the lens is functionally astigmatically neutral, and IOL misalignment greater than 30° can increase the cylindrical refractive error. In the FDA clinical trials for a plate-haptic toric IOL, 76% of lenses were within 10° of preoperative alignment, and 95% were within 30°. In the FDA clinical trials for the 1-piece acrylic toric IOL, the degree of postoperative rotation in 242 implanted eyes was 5° or less in 81.1% and 10° or less in 97.1%. None of the eyes exhibited postoperative rotation greater than 15°.
Typically, a misaligned IOL is recognized within days of the surgery; it should be repositioned before permanent fibrosis occurs within the capsular bag. However, waiting 1 week for some capsule contraction to occur may ultimately help stabilize this IOL. An online calculator is available to help determine the exact amount of IOL rotation necessary to optimize visual outcome (www.astigmatismfix.com).
Visser N, Ruíz-Mesa R, Pastor F, Bauer NJ, Nuijts RM, Montés-Micó R. Cataract surgery with toric intraocular lens implantation in patients with high corneal astigmatism. J Cataract Refract Surg. 2011;37(8):1403–1410.
Excerpted from BCSC 2020-2021 series: Section 13 - Refractive Surgery. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.