Accuracy of intraocular lens calculation formulas for flanged intrascleral intraocular lens fixation with double-needle technique

Purpose: To evaluate the refractive prediction error (RPE) of intraocular lens (IOL) calculation formulas in eyes that have undergone the Yamane technique for scleral fixation of IOLs. Setting: Alkek Eye Center, Cullen Eye Institute, Baylor College of Medicine, Houston, Texas. Design: Retrospective case series from electronic chart review. Methods: Patients who had undergone scleral fixation of secondary IOLs were selected. The IOL RPEs for 4 IOL prediction formulas - Barrett Universal II, Holladay 1, Hoffer Q, and SRK/T formulas - were obtained by subtracting the predicted spherical equivalent from the postoperative spherical equivalent. The arithmetic mean RPE, mean absolute error (MAE), and percentages of eyes with prediction error of 0.50 diopter (D) or lesser and 1.00 D or lesser were calculated and compared. Results: Forty eyes of 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 Universal II, 0.80 D for SRK/T, and 0.86 D for Hoffer Q formulas. The percentage of eyes with prediction error of 0.50 D or lesser and 1.00 D or lesser with these formulas were 45% (18 eyes) and 75% (30 eyes) for Holladay 1, 38.5% (15 eyes) and 77% (30 eyes) for Barrett Universal II, 32.5% (13 eyes) and 67.5% (27 eyes) for SRK/T, and 27.5% (11 eyes) and 62.5% (25 eyes) for Hoffer Q formulas. There were no statistically significant differences in prediction errors between the 4 formulas. Conclusions: Refractive outcomes of the Yamane technique were less predictable than those of standard cataract surgery. Arithmetic RPE ranged from hyperopic to predicted values for all formulas tested.