Refractive surprise after toric intraocular lens implantation: graph analysis.

PURPOSE To determine the refractive cylinder effect of rotating a toric intraocular lens (IOL) and identify the sources of refractive astigmatic surprise after toric IOL implantation. SETTING Private practice, Melbourne, Australia. DESIGN Experimental study. METHODS Vergence formulas using a standard reduced eye model were used to bring all lens powers to the corneal plane. Double-angle vector diagrams were then used to (1) determine the refractive cylinder effect of rotating a toric IOL and (2) show how the prevailing astigmatism and the various planning and surgical steps involved in implanting a toric IOL contribute to the postoperative manifest refractive cylinder. RESULTS An example calculation is given to illustrate the method. CONCLUSIONS Refractive cylinder surprises can occur after toric IOL implantation. Understanding the causes enables surgeons to address contributory factors and choose an appropriate surgical method for managing individual cases of refractive cylinder surprise. FINANCIAL DISCLOSURE Dr. Alpins and Mr. Stamatelatos have a financial interest in the Assort software program used to support the planning and analysis of astigmatic correction. Dr. Ong is an employee of Assort.