Nomogram-based intraocular lens power adjustment after myopic photorefractive keratectomy and LASIK - A new approach

Purpose: (1) To evaluate the accuracy of nomogram-based adjustment of intraocular lens (IOL) power to achieve a desired refractive target after cataract surgery in postmyopic LASIK and photorefractive keratectomy (PRK) eyes and (2) to compare the accuracy of the nomogram-based method with the clinical history method. Design: Multicenter, retrospective, interventional, noncomparative case series. Subjects: Fourteen patients (19 eyes) after myopic LASIK or PRK with visually significant cataracts. Intervention: All eyes underwent cataract extraction and posterior chamber intraocular lens implantation. In each case, IOL power was determined with standard keratometry and biometry. Power adjustment was made by use of a theoretical nomogram followed by implantation. Main Outcome Measures: (1) Final refraction and spherical equivalent after cataract surgery and (2) deviation of the final spherical equivalent from the refractive target. Results: After cataract extraction, by use of nomogram adjustment, 63.2% of eyes were within 0.5 D of the intended spherical equivalent, 84.2% were within 1.0 diopter of the intended spherical equivalent, and 100% were within 1.5 D of the intended spherical equivalent. The clinical history method was accurate in predicting the correct IOL power in 37.5% of cases, regardless of whether spectacle or corneal plane refraction was used. Conclusions: (1) Given the change in spherical equivalent induced by myopic LASIK/PRK, IOL power can be adjusted accurately to avoid undercorrection without the need for the prerefractive surgery corneal power. (2) The nomogram-based method was more accurate than the clinical history method.