Supplementary Material for: Accuracy of Constant C for Ray Tracing: Assisted Intraocular Lens Power Calculation in Normal Ocular Axial Eyes

<b><i>Objective:</i></b> To evaluate the effect of constant C for ray tracing-assisted intraocular lens (IOL) power calculation in patients with different refractive power, we compared the refractive outcome of the ray tracing method based on constant C and conventional IOL calculation. <b><i>Methods:</i></b> 215 eyes which underwent phacoemulsification and IOL implantation were enrolled in the study. According to the average corneal power, patients were divided into 3 groups: high corneal power (K &gt;45 D) group, medium corneal power (43 ≤ K ≤ 45 D) group, and low corneal power (K &lt;43 D) group. The predicted sphero-equivalent refractive outcome for the IOL power implanted at surgery was calculated using the ray tracing method, SRK/T, and Haigis formulas. <b><i>Results:</i></b> On the basis of the corneal refractive power, there were 65 eyes of K &gt;45 D (30.23%), 96 eyes of 43 ≤ K ≤ 45 D (44.65%), and 54 eyes of K &lt;43 D (25.12%). In general, the ray tracing group had the smallest value of mean absolute error (MAE) and mean error, and the proportions of eyes with absolute error (AE) &lt;0.50 and &lt;0.75 D were significantly higher than those of the other 2 formulas (<i>p</i> = 0.010). In each group, the value of MAE was smallest in the ray tracing group; for the proportions of AEs &lt;0.50 and &lt;0.75 D, the values in the ray tracing group were higher than those in the SRK/T and Haigis groups. Especially in the high and low corneal refractive groups, the proportion of AE &lt;0.25 D was also obviously higher, but only in the low corneal refractive power group, and the difference was statistically significant (<i>p</i> = 0.006). <b><i>Conclusions:</i></b> Compared with the conventional formulas, C constant of the ray tracing-assisted IOL power calculation has more accuracy for the patients with different corneal refractive powers. Ray tracing could provide better guidance for IOL selection clinically.