Induced Astigmatism

Localized change in corneal curvature may result from corneal burns produced by the phaco tip or, more commonly, from surgical incisions. Most well-constructed peripheral corneal, limbal, or scleral incisions that are less than 3 mm wide will induce less than 1.00 diopter (D) of astigmatism, usually flattening in the meridian of the incision. Larger incisions closer to the corneal apex or those that require suture closure are more likely to induce astigmatism. Tight radial sutures may steepen corneal curvature in the meridian of the suture.

The astigmatism induced by larger sutured incisions, such as those used in ICCE, ECCE, and secondary IOL implantation, may decrease by several diopters over time as the sutures dissolve or relax. When suture removal is needed to modulate astigmatism, waiting 6–8 weeks postoperatively is preferred. When more than 1 suture must be removed, it is preferable to cut adjacent sutures in a series of visits rather than all at once. Removal of too many sutures too early in the postoperative period may result in either significant corneal flattening in the meridian of the incision or wound dehiscence.

Excerpted from BCSC 2020-2021 series: Section 11 - Lens and Cataract. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.