Accuracy of Intraocular Lens Power Calculation Formulas Using Total Keratometry in Eyes With Previous Radial...

To evaluate the performance of intraocular lens (IOL) power calculation using standard keratometry (SK) and total keratometry (TK) in eyes after radial keratotomy (RK) surgery.

A retrospective, consecutive case series study included 49 patients with cataract (65 eyes) after RK. All implanted IOLs were monofocal in-the-bag lenses. Formulas using SK included American Society of Cataract and Refractive Surgery (ASCRS) average, Barrett True K, double-K modified Holladay 1 formula (DK-Holladay), Emmetropia Verifying Optical formula 2.0 (EVO 2.0), Holladay 1, Holladay 2, PEARL-DGS, and LISA formula for patients with cataract and prior myopic refractive surgery (LISA-MRS). Formulas using TK included Barrett True K-TK, EVO 2.0-TK, Holladay 2-TK, and LISA-MRS-TK. Holladay formulas used both Wang-Koch (Holladay-WK) and Holladay axial length (Holladay-AL) adjustment. The mean prediction error (PE), mean absolute PE (MAE), median absolute error (MedAE), root mean square absolute error (RMSAE), and the percentage of eyes within ±0.25, ±0.50, ±0.75, and ±1.00 diopters (D) of PE were evaluated.

In formulas using SK, the LISA-MRS formula exhibited the lowest MAE (0.71 D), lowest MedAE (0.52 D), and highest percentage of eyes within ±0.50 D of PE (49.23%). In formulas using TK, the LISA-MRS-TK formula exhibited the lowest MAE (0.78 D), lowest MedAE (0.48 D), and highest percentage of eyes within ±0.50 D of PE (52.63%). Using TK instead of SK significantly reduced the PE of both the Holladay 2 and LISA-MRS formulas. When AL was 30 mm or greater, the Holladay 1-AL formula exhibited the lowest MAE (0.68 D), lowest MedAE (0.32 D), and the highest percentage of eyes within ±0.50 D of PE (59.09%).

In post-RK eyes, the LISA-MRS formula displayed the highest prediction accuracy. TK could improve the prediction accuracy of the Holladay 2 and LISA-MRS formulas.