Calculation of Intralocular Lens Power Using Orbscan II Quantitative Area Topography After Corneal Refractive Surgery

PURPOSE: To present the prospective application of the Orbscan II central 2-mm total-mean corneal power obtained by quantitative area topography in intraocular lens (IOL) calculation after refractive surgery.METHODS: Calculated and achieved refraction and the difference between them were studied in 77 eyes of 61 patients with previous radial keratotomy (RK), RK and additional surgeries, myopic LASIK, myopic photo-refractive keratectomy (PRK), or hyperopic LASIK who underwent phacoemulsification without complications in 3 eye centers. All IOL calculations used the average from the central 2-mm Orbscan II total-mean power of maps centered on the pupil without the use of previous refractive data. Six IOL styles implanted within the bag were used.RESULTS: Using the SRK-T formula, the overall calculated refraction was -0.64 +/- 0.93 diopters (D). the overall achieved spherical equivalent refraction (-0.52 +/- 0.79 D; range: -3.12 to 1.25 D; 95% confidence interval [Cl]: -0.70/-0.34 D) was +/- 0.50 D in 53% of eyes, +/- 1.00 D in 78% of eyes and +/- 2.00 D in 99% of eyes the over-all difference between the calculated and achieved refraction (0.12 +/- 0.93 D, P=.27; range: -2.18 to 2.62 D; 95% Cl: 0.09/0.33 D) was +/- 0.50 D in 39% of eyes, +/- 1.00 D in 77% of eyes, and +/- 2.00 D in 96% of eyes. This difference was +/- 1.00 D in 77% of eyes with RK (P=.70), 82% of eyes with myopic LASIK (P=.34) and, 90% of eyes with myopic PRK (P=.96). in eyes with RK followed by LASIK, a trend toward undercorrection was noted (P=.03). in eyes with hyperopic LASIK, a trend toward overcorrection was noted (P=.005).CONCLUSIONS: in eyes with previous corneal refractive surgery, IOL power calculation can be performed with reasonable accuracy using the Orbscan II central 2-mm total-mean power. This method had better outcomes in eyes with previous RK, myopic LASIK, and myopic PRK than in eyes with hyperopic LASIK or RK with LASIK [J Refract Surg. 2009;25:1061-1074.] doi: 10.3928/1081597X-20091117-05Universidade Federal de São Paulo, Paulista Sch Med, Dept Ophthalmol, Inst Vis,Ocular Bioengn Sector, São Paulo, BrazilUniversidade Federal de São Paulo, Paulista Sch Med, Dept Ophthalmol, Inst Vis,Refract Surg Sector, São Paulo, BrazilSUNY Syracuse, Upstate Med Ctr, Dept Ophthalmol, Syracuse, NY USAPiedmont Better Vis LLC, Atlanta, GA USAUniversidade Federal de São Paulo, Paulista Sch Med, Dept Ophthalmol, Inst Vis,Cataract Sector, São Paulo, BrazilUniversidade Federal de São Paulo, Paulista Sch Med, Dept Ophthalmol, Inst Vis,Ocular Bioengn Sector, São Paulo, BrazilUniversidade Federal de São Paulo, Paulista Sch Med, Dept Ophthalmol, Inst Vis,Refract Surg Sector, São Paulo, BrazilUniversidade Federal de São Paulo, Paulista Sch Med, Dept Ophthalmol, Inst Vis,Cataract Sector, São Paulo, BrazilWeb of Scienc