Comparison of intraocular lens calculation methods after myopic laser-assisted in situ keratomileusis and radial keratotomy without prior refractive data

Aim To compare intraocular lens (IOL) calculation methods not requiring refraction data prior to myopic laser-assisted in situ keratomileusis (LASIK) and radial keratotomy (RK). Methods In post-LASIK eyes, the methods not requiring prior refraction data were Hagis-L; Shammas; Barrett True-K no-history; Wang-Koch-Maloney; 'average', 'minimum' and 'maximum' IOL power on the American Society of Cataract and Refractive Surgeons (ASCRS) IOL calculator. Double-K method and Barrett True-K no-history, 'average', 'minimum' and 'maximum' IOL power on ASCRS IOL calculator were evaluated in post-RK eyes. The predicted IOL power was calculated with each method using the manifest postoperative refraction. Arithmetic and absolute IOL prediction errors (PE) (implanted-predicted IOL powers), variances in arithmetic IOL PE and percentage of eyes within +/- 0.50 and +/- 1.00 D of refractive PE were calculated. Results Arithmetic or absolute IOL PE were not significantly different between the methods in post-LASIK and post-RK eyes. In post-LASIK eyes, 'average' showed the highest and 'minimum' showed the least variance, whereas 'average' and 'minimum' had highest percentage of eyes within +/- 0.5 D and 'minimum' had the highest percentage of eyes within +/- 1.0 D. In the post-RK eyes, 'minimum' had highest variance, and 'average' had the least variance and highest percentage of eyes within +/- 0.5 D and +/- 1.0 D. Conclusion In post-LASIK and post-RK eyes, there are no significant differences in IOL PE between the methods not requiring prior refraction data. 'Minimum' showed least variance in PEs and more chances of eyes to be within +/- 1.0 D postoperatively in post-LASIK eyes. 'Average' had least variance and more chance of eyes within +/- 1.0 D in post-RK eyes.