Accuracy of Intraocular Lens Calculation Formulas for Flanged Intrascleral Intraocular Lens Fixation with Double-Needle Technique

Purpose To evaluate the refractive prediction error of intraocular lens calculation formulas in eyes that have undergone the Yamane technique for scleral fixation of intraocular lenses (IOL). Setting Alkek Eye Center, Cullen Eye Institute, Baylor College of Medicine, Houston, TX DESIGN:: Retrospective case series from electronic chart review. Methods Patients who had undergone scleral fixation of secondary IOLs were selected. The IOL refractive prediction errors (RPE) for 4 IOL prediction formulas - Barrett Universal II, Holladay 1, Hoffer-Q, and SRK/T - were obtained by subtracting the predicted spherical equivalent from post-operative spherical equivalent. The arithmetic mean RPE, mean absolute error (MAE), and percentages of eyes with prediction error of ≤0.5 D and ≤1.0 D were calculated and compared. Results 40 eyes of the 40 patients met inclusion criteria. All formulas produced hyperopic mean arithmetic RPE. MAE values were 0.73 D for Holladay 1, 0.76 D for Barrett, 0.80 D for SRK/T, and 0.86 D for Hoffer Q. The percentage of eyes with prediction error of ≤0.5 D and ≤1.0 D with these formulas were: 45% (18 eyes) and 75% (30 eyes) for Holladay 1, 38.5% (15 eyes) and 77% (30 eyes) for Barrett, 32.5% (13 eyes) and 67.5% (27 eyes) for SRK/T, and 27.5% (11 eyes) and 62.5% (25 eyes) with Hoffer-Q. There were no significant differences in prediction errors between the 4 formulas. Conclusion Refractive outcomes of the Yamane technique are less predictable than standard cataract surgery. Arithmetic RPE is hyperopic to predicted for all formulas tested.