Accuracy of Different Intraocular Lens Calculation Formulas in Patients with High Axial Myopia

Background The two main problems encountered in calculation of intra ocular lens power are the measurement of the proper axial length (AL), and the lack of accuracy of the available formulas that calculate the power of the intra ocular lens in cases of eyes with high axial length. Aim of the Work To compare the accuracy of intraocular lens (IOL) calculation formulae (Holladay I, Haigis, SRK/T, Hoffer Q, Holladay II, and Barrett Universal II) in the prediction of postoperative refraction for eyes with AL 26.0 mm or more. Patients and Methods A prospective study was carried on forty-seven eyes of forty-seven patients. All the patients were managed at Ain Shams University Hospitals in cooperation with a specialized centre between April 2019 and March 2020. Results Mean absolute error (MAE) was calculated for each formula showed that the least MAE is for Barrett Universal II formula. SRK/T formula is the 2nd lower MAE followed by Haigis formula and the last is Holladay II formula. The scatter plots between AL and absolute error from each of the six calculations formulae was done and showed that Barrett universal II has negative correlation with AL. As for SRK/T and Haigis formulae there is a linear correlation. Numerical Predictive Error showed that SRK/T formula had the lowest mean numerical error followed by Haigis formula then Barrett Universal II and last came Holladay II formula. Conclusion for high axial myopic eyes, the Barrett Universal II formula is the best in this group of patients and provide the lowest mean absolute error, highest percentage of eyes within ≤ ± 0.50 D and the lowest risk of refractive surprise compared to other IOL power calculation formulae. Then comes Haigis and SRK/T formulae which performed similarly and provide a good predictable outcome then at last came Holladay II formula.